Process for dyeing keratin fibres using at least one particular 2- or 4-azopyridinium dye and at least one fluorescent dye

ABSTRACT

The present invention relates to a process for dyeing keratin fibres, in particular human keratin fibres such as the hair, using one or more particular 2- or 4-azopyridinium dyes and one or more fluorescent dyes. The present invention also relates to a cosmetic composition comprising the dyes defined above, and also to a multi-compartment device containing said dyes. The present invention also relates to the use of said dyes for dyeing light keratin fibres, especially human keratin fibres such as the hair, in chestnut-brown, dark chestnut-brown, brown, brown with a glint, or even black, without using an additional dye other than those defined above.

The present invention relates to a process for dyeing keratin fibres, in particular human keratin fibres such as the hair, using one or more particular 2- or 4-azopyridinium dyes and one or more fluorescent dyes.

The present invention also relates to a cosmetic composition comprising the dyes defined above, and also to a multi-compartment device containing said dyes.

The present invention also relates to the use of said dyes for dyeing light keratin fibres, especially human keratin fibres such as the hair, in chestnut-brown, dark chestnut-brown, brown, brown with a glint, or even black, without using an additional dye other than those defined above.

Many people have sought for a long time to modify the colour of their hair and in particular to mask their grey hair.

It is especially known practice to dye keratin fibres, in particular human keratin fibres, with dye compositions containing oxidation dye precursors, which are generally known as oxidation bases. These oxidation bases are colourless or weakly coloured compounds, which, when combined with oxidizing products, may give rise to coloured compounds via a process of oxidative condensation.

The shades obtained with these oxidation bases may be modified by combining them with couplers or colour modifiers. The variety of molecules used as oxidation bases and couplers allows a wide range of colours to be obtained.

Another well-known method consists in obtaining semi-permanent dyeing by applying to the keratin fibres direct dyes, which are coloured and colouring molecules that have affinity for said fibres.

The direct dyes conventionally used are chosen from nitrobenzene, anthraquinone, nitropyridine, azo, xanthene, acridine, azine and triarylmethane direct dyes. The chemical species may be nonionic, anionic (acidic dyes) or cationic (basic dyes). The direct dyes may also be natural dyes.

Conventional direct dyeing processes consist in applying to keratin fibres dye compositions comprising direct dyes. After application, a leave-on time is observed so as to allow the colouring molecules to penetrate by diffusion into the fibres. On conclusion of the process, the fibres are rinsed.

In contrast with oxidation dyeing, these direct dyeing processes have a tendency to better protect the integrity of the fibres. The resulting colourings are generally chromatic, but, however, are only semi-temporary. The nature of the interactions that bind the direct dyes to the keratin fibres and their desorption from the surface and/or the core of the fibre are responsible for their weak dyeing power.

Although a wide range of colours is currently accessible, it generally proves necessary to combine three dyes of complementary colours—trichromatic principle—in order to obtain a natural shade (see, for example, WO 95/15144 and WO 95/01772). This tripartite combination does not, however, show good persistence with respect to repeated shampooing. It generally, or even systematically, induces an unaesthetic changing of the colour, which the consumer finds dissuasive.

These colourings are furthermore not sufficiently fast in the face of external agents such as light or perspiration.

Thus, there is a real need to develop processes for the direct dyeing of keratin fibres, in particular of human keratin fibres such as the hair, which do not have the drawbacks mentioned above, i.e. which make it possible especially to lead to natural colourings that have good properties, especially in terms of chromaticity, power, intensity, sheen and selectivity, and which are persistent with respect to shampooing.

Another aim of the present invention is thus to be able to dye light keratin fibres efficiently in chestnut-brown, dark chestnut-brown, brown or brown with a glint or even black, by mixing direct dyes, and preferably only two types of direct dye.

The Applicant has found, surprisingly, that a process for dyeing keratin fibres using one or more particular 2- or 4-azopyridinium dyes and one or more fluorescent dyes makes it possible to achieve the objectives mentioned above; especially to lead to natural chestnut-brown, dark chestnut-brown, brown, brown with a glint or even black colourings, which are not only powerful and shiny, but also shampoo-resistant.

One subject of the present invention is especially a process for dyeing keratin fibres, in particular human keratin fibres such as the hair, comprising the application to said keratin fibres of the following ingredients: (a) one or more 2- or 4-azopyridinium dyes chosen from the compounds of formula (I) or (II) below, the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof,

in which formulae (I) and (II):

-   -   R₁ and R′₁, which may be identical or different, represent an         optionally substituted linear or branched C₁ to C₆ alkyl         radical;     -   R₂ and R′₂, which may be identical or different, represent:         -   a halogen atom, preferentially a chlorine atom, or         -   a linear or branched C₁ to C₄ alkyl radical;     -   R₃ and R′₃, which may be identical or different, represent,         independently of each other:         -   a C₁ to C₄ alkyl radical, preferably methyl or ethyl,         -   a (di)(C₁-C₄)(alkyl)amino radical,         -   a (C₁-C₄)alkylcarbonylamino radical, preferably acylamino             (—NHCOCH₃),         -   a hydroxyl radical,         -   a halogen atom, preferably a chlorine atom,         -   a C₁ to C₄ alkoxy radical, preferably methoxy or ethoxy,         -   a (C₁-C₄)alkylthio radical,         -   or alternatively, two adjacent radicals R₃ or R′₃ together             form a 6-membered aromatic ring optionally substituted with             one or more hydroxyl or amino groups;     -   R₄ and R′₄, which may be identical or different, represent:         -   a (di)(C₁-C₄)(alkyl)amino radical,         -   a hydroxyl radical,         -   a C₁ to C₄ alkoxy radical, preferably methoxy or ethoxy,         -   a radical —NR₅R₆, in which R₅ and R₆, which may be identical             or different, represent, independently of each other:             -   a linear or branched, optionally substituted C₁ to C₂₀                 alkyl radical, or             -   a phenyl radical;         -   or alternatively, two radicals R₃ of formula (I) or R′₃ of             formula (II) located, respectively, ortho to the group R₄             (formula (I)) or R′₄ (formula (II)) form, respectively, with             R₅ and R₆ of the group R₄ (formula (I)) or of the group R′₄             (formula (II)) a 6- to 10-membered heterocycle optionally             comprising one or more heteroatoms, preferably the phenyl             group substituted with R₃ and R₄ or R′₃ and R′₄ represents a             julolidine group;     -   m, m′, n and n′ are integers ranging from 0 to 4;     -   Y represents an anionic counterion or a mixture of organic or         inorganic anions which ensure the electrical neutrality of the         compounds of formula (I) and/or (II); and (b) one or more         fluorescent dyes;         it being understood that the 2- or 4-azopyridinium dye(s) (a)         and the fluorescent dye(s) (b) are applied to said keratin         fibres together or sequentially.

Another subject of the invention is a cosmetic composition comprising: (a) one or more 2- or 4-azopyridinium dyes chosen from the compounds of formula (I) or (II) as defined previously, and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof; and (b) one or more fluorescent dyes.

The combination of particular 2- or 4-azopyridinium dye(s) and of fluorescent dye(s) makes it possible especially to obtain natural colourings that have good dyeing properties, especially in terms of chromaticity, power, intensity, sheen and selectivity.

Furthermore, the process and the composition according to the invention make it possible to dye light keratin materials efficiently in chestnut-brown, dark chestnut-brown, brown, brown with a glint or even black, by mixing direct dyes, and in particular only the dyes (a) and (b) as defined previously, without the need to use an additional (or complementary) dye other than (a) or (b).

Moreover, the colourings obtained by means of the process and the composition according to the invention show good resistance to the various attacking factors to which the hair may be subjected, such as light, bad weather, washing and perspiration. They are in particular persistent with respect to shampooing, especially after at least three shampoo washes.

A subject of the present invention is also a multi-compartment device comprising a first compartment containing one or more 2- or 4-azopyridinium dyes (a) chosen from the compounds of formula (I) or (II) as defined previously, and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof, and a second compartment containing one or more fluorescent dyes (b) as defined previously.

Another subject of the invention is the use of fluorescent dye(s), as defined previously, combined with 2- or 4-azopyridinium dye(s) chosen from the compounds of formula (I) or (II), as defined previously, and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof, for the dyeing of light keratin fibres, especially human keratin fibres such as the hair, in chestnut-brown, dark chestnut-brown, brown, brown with a glint or even black, without using an additional dye other than (a) or (b).

Other subjects, characteristics, aspects and advantages of the invention will emerge even more clearly on reading the description and the examples that follow.

For the purposes of the present invention and unless otherwise indicated:

-   -   the “dyes” according to the invention absorb light in the         visible range, i.e. at a wavelength λ_(abs) particularly of         between 400 and 700 nm inclusive;     -   for the purposes of the present invention, the term “direct dye”         means natural and/or synthetic dyes, which are soluble in the         cosmetic medium, other than oxidation dyes; they are dyes which         will diffuse superficially on the keratin fibres;     -   for the purposes of the present invention, the term “fluorescent         dye” means a dye which is a coloured molecule (which absorbs         visible light) and which itself imparts colour, and which, in         contrast with a conventional dye, transforms the absorbed energy         into light of a longer wavelength emitted in the visible part of         the spectrum; in particular, the “fluorescent” dyes of the         invention are capable of absorbing light in the visible range at         a wavelength λ_(abs) of between 350 and 800 nm and of         re-emitting in the visible range at a longer wavelength λ_(em)         than that absorbed, of between 400 and 800 nm; the difference         between the absorption and emission wavelengths, also known as         the Stoke's shift, is between 1 nm and 100 nm. More         preferentially, the fluorescent dyes of the invention are dyes         that are capable of absorbing at a wavelength λ_(abs) of between         420 nm and 550 nm and of re-emitting in the visible range at a         wavelength λ_(cm) of between 470 and 600 nm;     -   the “fluorescent dyes” according to the present invention are to         be differentiated from optical brighteners. Optical brighteners,         also known as “brighteners” or “fluorescent brighteners” or         “fluorescent brightening agents” or “fluorescent whitening         agents or FWA” or “whiteners” or “fluorescent whiteners”, are         colourless compounds, which do not impart a colour and are         consequently not dyes since they do not absorb in the visible         light range, but only absorb in the ultraviolet range         (wavelength ranging from 200 to 400 nm) and transform the         absorbed energy into fluorescent light of a longer wavelength         emitted in the visible part of the spectrum in the blue range.         The colour impression is then generated only by the purely         fluorescent light that is predominantly blue (wavelength ranging         from 400 to 500 nm).     -   the “blue, violet and green” dyes according to the invention are         dyes which absorb light in the visible spectrum and which appear         blue visually, i.e. which absorb light at an absorption         wavelength λ_(max) greater than 550 nm and less than or equal to         700 nm, in particular λ_(max) between 560 nm and 700 nm,         preferably in the blue range, i.e. λ_(max) between 580 and 650         nm;     -   the term “(hetero)aryl” means aryl and heteroaryl groups;     -   the “aryl” or “heteroaryl” radicals or the aryl or heteroaryl         part of a radical may be substituted with at least one         substituent borne by a carbon atom, chosen from:     -   a C₁-C₆ and preferably C₁-C₄ alkyl radical optionally         substituted with one or more radicals chosen from hydroxyl,         C₁-C₂ alkoxy, C₂-C₄ (poly)hydroxyalkoxy, acylamino, amino         substituted with two C₁-C₄ alkyl radicals, which may be         identical or different, optionally bearing at least one hydroxyl         group, or the two radicals possibly forming, with the nitrogen         atom to which they are attached, a saturated or unsaturated,         optionally substituted 5- to 7-membered and preferably 5- or         6-membered heterocycle optionally comprising another nitrogen or         non-nitrogen heteroatom;     -   a halogen atom such as chlorine;     -   a hydroxyl or thiol group;     -   a C₁-C₆ alkoxy or C₁-C₆ alkylthio radical;     -   a (poly)hydroxy(C₂-C₆)alkoxy radical;     -   an amino radical;     -   a 5- or 6-membered heterocycloalkyl radical, preferentially         morpholino, piperazino, piperidino or pyrrolidino, which is         optionally substituted with a (C₁-C₄) alkyl radical,         preferentially methyl;     -   a 5- or 6-membered heteroaryl radical, preferentially         imidazolyl, optionally substituted with a (C₁-C₄)alkyl radical,         preferentially methyl;     -   an amino radical substituted with one or two identical or         different C₁-C₆ alkyl radicals, optionally bearing at least:     -   i) a hydroxyl group,     -   ii) an amino group optionally substituted with one or two         optionally substituted C₁-C₃ alkyl radicals, said alkyl radicals         possibly forming with the nitrogen atom to which they are         attached a saturated or unsaturated, optionally substituted 5-         to 7-membered heterocycle, optionally comprising at least one         other nitrogen or non-nitrogen heteroatom,     -   iii) a quaternary ammonium group —N+R′R″R″′, M⁻ for which R′, R″         and R″′, which may be identical or different, represent a C₁-C₄         alkyl group and M-represents an anionic counterion,     -   iv) or an optionally cationic 5- or 6-membered heteroaryl         radical, preferentially imidazolium, optionally substituted with         a (C₁-C₄)alkyl radical, preferentially methyl;     -   an acylamino radical (—N(R)—C(O)—R′) in which the radical R is a         hydrogen atom or a C₁-C₄ alkyl radical optionally bearing at         least one hydroxyl group and the radical R′ is a C₁-C₂ alkyl         radical;     -   a carbamoyl radical ((R)₂N—C(O)—) in which the radicals R, which         may be identical or different, represent a hydrogen atom or a         C₁-C₄ alkyl radical optionally bearing at least one hydroxyl         group;     -   an alkylsulfonylamino radical (R′—S(O)₂—N(R)—) in which the         radical R represents a hydrogen atom or a C₁-C₄ alkyl radical         optionally bearing at least one hydroxyl group and the radical         R′ represents a C₁-C₄ alkyl radical, or a phenyl radical;     -   an aminosulfonyl radical ((R)₂N—S(O)₂—) in which the radicals R,         which may be identical or different, represent a hydrogen atom         or a C₁-C₄ alkyl radical optionally bearing at least one         hydroxyl group;     -   a carboxyl radical in acid or salified form (preferably salified         with an alkali metal or a substituted or unsubstituted         ammonium);     -   a cyano group;     -   a nitro or nitroso group;     -   a polyhaloalkyl group, preferentially trifluoromethyl;     -   the cyclic or heterocyclic part of a non-aromatic radical may be         substituted with at least one substituent chosen from the         following groups:     -   hydroxyl;     -   C₁-C₄ alkoxy, (poly)hydroxy(C₂-C₄)alkoxy;     -   C₁-C₄ alkyl;     -   alkylcarbonylamino (R—C(O)—N(R′)—) in which the radical R′ is a         hydrogen atom or a C₁-C₄ alkyl radical optionally bearing at         least one hydroxyl group, and the radical R is a C₁-C₂ alkyl         radical or an amino radical optionally substituted with one or         two C₁-C₄ alkyl groups, which may be identical or different,         themselves optionally bearing at least one hydroxyl group, said         alkyl radicals possibly forming, with the nitrogen atom to which         they are attached, a saturated or unsaturated, optionally         substituted 5- to 7-membered heterocycle optionally comprising         at least one other nitrogen or non-nitrogen heteroatom;     -   alkylcarbonyloxy (R—C(O)—O—) in which the radical R is a C₁-C₄         alkyl radical or an amino group optionally substituted with one         or two identical or different C₁-C₄ alkyl groups themselves         optionally bearing at least one hydroxyl group, said alkyl         radicals possibly forming with the nitrogen atom to which they         are attached a saturated or unsaturated, optionally substituted         5- to 7-membered heterocycle, optionally comprising at least one         other nitrogen or non-nitrogen heteroatom;     -   alkoxycarbonyl (R—X—C(O)—) in which the radical R is a C₁-C₄         alkoxy radical, X is an oxygen atom or an amino group optionally         substituted with a C₁-C₄ alkyl group itself optionally bearing         at least one hydroxyl group, said alkyl radical possibly forming         with the nitrogen atom to which it is attached a saturated or         unsaturated, optionally substituted 5- to 7-membered         heterocycle, optionally comprising at least one other nitrogen         or non-nitrogen heteroatom;     -   a cyclic or heterocyclic radical, or a non-aromatic part of an         aryl or heteroaryl radical, which may also be substituted with         one or more oxo groups;     -   an “aryl” radical represents a monocyclic or fused or non-fused         polycyclic carbon-based group comprising from 6 to 22 carbon         atoms, at least one ring of which is aromatic; preferentially,         the aryl radical is a phenyl, biphenyl, naphthyl, indenyl,         anthracenyl or tetrahydronaphthyl;     -   a “cationic heteroaryl radical” is a heteroaryl group as defined         previously, which comprises an endocyclic or exocyclic cationic         group,         -   when the charge is endocyclic, it is included in the             electron delocalization via the mesomeric effect; for             example, it is a pyridinium, imidazolium or indolinium             group:

-   -   -   with R and R′ being a heteroaryl substituent as defined             previously and particularly a (hydroxy)(C₁-C₅)alkyl group,             such as methyl;         -   when the charge is exocyclic, it is not included in the             electron delocalization via the mesomeric effect; for             example, it is an ammonium or phosphonium substituent R⁺,             such as trimethylammonium, which is outside the heteroaryl,             such as pyridyl, indolyl, imidazolyl or naphthalimidyl, in             question:

-   -   -   with R being a heteroaryl substituent as defined below and             R⁺ an ammonium R_(a)R_(b)R_(c)N⁺—, phosphonium             R_(a)R_(b)R_(c)P⁺— or ammonium R_(a)R_(b)R_(c)N⁺—             (C₁-C₆)alkylamino, R_(a)R_(b)R_(c)N⁺—(C₁-C₆)alkyl or             R_(a)R_(b)R_(c)N⁺—(C₁-C₆)alkoxy group with R_(a), R_(b) and             R_(c), which may be identical or different, being a             (C₁-C₈)alkyl group such as methyl;

    -   a “heteroaryl radical” represents a 5- to 22-membered,         monocyclic or fused or non-fused polycyclic group, comprising         from 1 to 6 heteroatoms chosen from nitrogen, oxygen and sulfur,         at least one ring of which is aromatic; preferentially, a         heteroaryl radical is chosen from acridinyl, benzimidazolyl,         benzobistriazolyl, benzopyrazolyl, benzopyridazinyl,         benzoquinolyl, benzothiazolyl, benzotriazolyl, benzoxazolyl,         pyridinyl, tetrazolyl, dihydrothiazolyl, imidazopyridinyl,         imidazolyl, indolyl, isoquinolyl, naphthoimidazolyl,         naphthoxazolyl, naphthopyrazolyl, oxadiazolyl, oxazolyl,         oxazolopyridyl, phenazinyl, phenoxazolyl, pyrazinyl, pyrazolyl,         pyrilyl, pyrazoyltriazyl, pyridyl, pyridinoimidazolyl, pyrrolyl,         quinolyl, tetrazolyl, thiadiazolyl, thiazolyl,         thiazolopyridinyl, thiazoylimidazolyl, thiopyrylyl, triazolyl,         xanthylyl and the ammonium salt thereof;

    -   a “heterocyclic radical” is a radical which may contain one or         two unsaturations, but is a monocyclic or fused or non-fused         polycyclic, 5- to 22-membered non-aromatic radical comprising         from 1 to 6 heteroatoms chosen from nitrogen, oxygen and sulfur;

    -   a “heterocycloalkyl radical” is a heterocyclic radical         comprising at least one saturated ring;

    -   an “alkyl radical” is a linear or branched C₁ to C₂₀, preferably         C₁ to C₁₀, more preferentially C₁ to C₈, better still C₁ to C₆         and even better still C₁ to C₄ hydrocarbon-based radical;

    -   the expression “optionally substituted” applied to the alkyl         radical implies that said alkyl radical may be substituted with         one or more radicals chosen from the following radicals: i)         hydroxyl, ii) C₁-C₄ alkoxy, iii) R—Z—C(X)—Y— with X, Y and Z         representing an oxygen or sulfur atom or N(R′), or alternatively         X and/or Z represent a bond, R and R′, which may be identical or         different, represent a hydrogen atom or a (C₁-C₆)alkyl group,         preferably, X represents an oxygen atom, iv) amino optionally         substituted with one or two identical or different C₁-C₄ alkyl         radicals, said alkyl radicals possibly forming, with the         nitrogen atom that bears them, a 5- to 7-membered heterocycle,         optionally comprising another nitrogen or non-nitrogen         heteroatom; v) or a quaternary ammonium group N+R′R″R″′, M⁻ for         which R′, R″ and R″′, which may be identical or different,         represent a C₁-C₄ alkyl group, or alternatively —N⁺R′R″R″′ forms         a heteroaryl such as imidazolium optionally substituted with a         C₁-C₄ alkyl group and M⁻ represents the anionic counterion, vi)         carboxyl C(O)OH, vii) carboxylate C(O)O—, M⁺ with M⁺         representing a cationic counterion such as alkali metal or         alkaline-earth metal, viii) sulfonic —SO₃H, ix) sulfonate —SO₃         ⁻, M⁺ with M⁺ as defined previously, x) cyano and xi) phenyl;

    -   an “alkoxy radical” is an alkyl-oxy radical for which the alkyl         radical is a linear or branched C₁-C₈ and preferentially C₁-C₆         hydrocarbon-based radical;

    -   when the alkoxy group is optionally substituted, this implies         that the alkyl group is optionally substituted as defined above;

    -   the term “organic or mineral acid salt” more particularly means         the salts chosen from a salt derived from i) hydrochloric acid         HCl, ii) hydrobromic acid HBr, iii) sulfuric acid H₂SO₄, iv)         alkylsulfonic acids: Alk-S(O)₂OH such as methanesulfonic acid         and ethanesulfonic acid; v) arylsulfonic acids: Ar—S(O)₂OH such         as benzenesulfonic acid and toluenesulfonic acid; vi) citric         acid; vii) succinic acid; viii) tartaric acid; ix) lactic         acid; x) alkoxysulfinic acids: Alk-O—S(O)—OH such as         methoxysulfinic acid and ethoxysulfinic acid; xi)         aryloxysulfinic acids such as tolueneoxysulfinic acid and         phenoxysulfinic acid; xii) phosphoric acid H₃PO₄; xiii) acetic         acid CH₃C(O)—OH; xiv) triflic acid CF₃SO₃H; and xv)         tetrafluoroboric acid HBF₄;

    -   the term “anionic counterion” means an anion or an anionic group         derived from an organic or mineral acid which counterbalances         the cationic charge of the dye; more particularly, the anionic         counterion is chosen from: i) halides such as chloride or         bromide; ii) nitrates; iii) sulfonates, including C₁-C₆         alkylsulfonates: Alk-S(O)₂O⁻ such as methylsulfonate or mesylate         and ethylsulfonate; iv) arylsulfonates: Ar—S(O)₂O⁻ such as         benzenesulfonate and toluenesulfonate or tosylate; v)         carboxylates Alk-C(O)—OH with Alk representing a (C₁-C₆)alkyl         group optionally substituted with one or more hydroxyl or         carboxylate groups such as citrate; vi) succinate; vii)         tartrate; viii) lactate; ix) alkyl sulfates: Alk-O—S(O)O⁻ such         as methyl sulfate and ethyl sulfate; x) aryl sulfates:         Ar—O—S(O)O⁻ such as benzene sulfate and toluene sulfate; xi)         alkoxy sulfates: Alk-O—S(O)₂O⁻ such as methoxy sulfate and         ethoxy sulfate; xii) aryloxy sulfates: Ar—O—S(O)₂O⁻, xiii)         phosphates O═P(OH)₂—O⁻, O═P(O⁻)₂—OH, O═P(O⁻)₃,         HO—[P(O)(O⁻)]_(w)—P(O)(O⁻)₂ with w being an integer; xiv)         acetate; xv) triflate; and xvi) borates such as         tetrafluoroborate, and xvii) sulfate (O=)₂S(O⁻)₂ or SO₄ ²⁻ and         hydrogen sulfate HSO₄ ⁻;

    -   the anionic counterion, derived from the organic or mineral acid         salt, ensures the electrical neutrality of the molecule; thus,         it is understood that when the anion comprises several anionic         charges, then the same anion may serve for the electrical         neutrality of several cationic groups in the same molecule or         else may serve for the electrical neutrality of several         molecules; for example, a dye which contains two cationic groups         may contain either two “singly charged” anionic counterions or a         “doubly charged” anionic counterion such as (O═)₂S(O⁻)₂ or         O═P(O⁻)₂—OH;

    -   In particular, the anionic counterions are chosen from halides         such as chloride, bromide, fluoride or iodide; a hydroxide; a         sulfate; a hydrogen sulfate; a linear or branched C₁-C₆ alkyl         sulfate, such as the methyl sulfate or ethyl sulfate ion;         carbonates and hydrogen carbonates; carboxylic acid salts such         as formate, acetate, citrate, tartrate and oxalate; linear or         branched C₁-C₆ alkylsulfonates, such as the methylsulfonate ion;         arylsulfonates for which the aryl part, preferably phenyl, is         optionally substituted with one or more C₁-C₄ alkyl radicals,         for instance 4-tolylsulfonate; and alkylsulfonates such as         mesylate;

    -   The term “chemical oxidizing agent” means any oxidizing agent         other than atmospheric oxygen conventionally used in the field.         Thus, mention may be made of hydrogen peroxide, urea peroxide,         alkali metal bromates, persalts such as perborates and         persulfates, and also enzymes, among which mention may be made         of peroxidases, 2-electron oxidoreductases such as uricases, and         4-electron oxygenases such as laccases. Preferably, the chemical         oxidizing agent is hydrogen peroxide;

    -   Moreover, the addition salts that may be used in the context of         the invention are especially chosen from salts of addition with         a cosmetically acceptable base such as the basifying agents as         defined below, for instance alkali metal hydroxides, such as         sodium hydroxide or potassium hydroxide, aqueous ammonia, amines         or alkanolamines;

    -   the expression “at least one” is equivalent to “one or more”;

    -   the limits of a range of values are included in that range, in         particular in the expressions “between” and “ranging from . . .         to . . . ”; and

    -   the expression “inclusive” for a range of values means that the         limits of that range are included in the defined range.

    -   (a) 2- or 4-azopyridinium Dyes

The process for dyeing keratin fibres and the cosmetic composition according to the present invention use, or comprise, (a) one or more 2- or 4-azopyridinium dyes chosen from the compounds of formula (I) or (II) as defined previously, the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof.

In particular, the dyes of formula (I) or (II) are blue, violet or green, and dull or chromatic.

When m, m′, n and n′ are less than 4, then the remaining carbon atom(s) are substituted with a hydrogen atom.

Preferably, R₁ and R′₁, which may be identical or different, represent a linear C₁ to C₆ alkyl radical, optionally substituted with one or more hydroxyl groups, and more preferentially a linear C₁ to C₆ alkyl group, optionally substituted with a hydroxyl group, such as a methyl, hexyl or hydroxyhexyl group.

Preferably, m and m′ are equal to 0 or 1, and R₂ and R′₂, independently of each other, represent a chlorine atom or a methyl group.

Preferably, R₄ and R′₄, which may be identical or different, represent:

-   -   an amino radical, or     -   a radical —NR₅R₆, in which R₅ and R₆, which may be identical or         different, represent, independently of each other:     -   a linear or branched C₁ to C₆ and more preferentially C₁ to C₄         alkyl radical, optionally substituted with one or more hydroxyl         groups, or     -   a phenyl radical.

According to a particular embodiment, R₁, R′₁, R₂, R′₂ and Y are as defined previously, and

-   -   R₃ and R′₃, which may be identical or different, represent,         independently of each other:         -   a C₁ to C₂ alkyl radical,         -   an amino radical,         -   an acylamino radical (—NHCOCH₃),         -   a chlorine atom,         -   a C₁ to C₂ alkoxy radical,         -   or alternatively, two adjacent radicals R₃ or R′₃ together             form a 6-membered aromatic ring optionally substituted with             a hydroxyl or amino group,         -   or alternatively, two radicals R₃ of formula (I) or R′₃ of             formula (II) located, respectively, ortho to the group R₄             (formula (I)) or R′₄ (formula (II)) form, respectively, with             R₅ and R₆ of the group R₄ (formula (I)) or of the group R′₄             (formula (II)) a 6- to 10-membered heterocycle comprising             one or two heteroatoms such as nitrogen, preferably the             phenyl group substituted with R₃ and R₄ or R′₃ and R′₄             represents a julolidine group; and     -   R₄ and R′₄, which may be identical or different, represent:     -   an amino radical, or     -   a radical —NR₅R₆, in which R₅ and R⁶, which may be identical or         different, represent, independently of each other:         -   a linear or branched C₁ to C₄ alkyl radical, optionally             substituted with one or more hydroxyl groups, or         -   a phenyl radical.

Advantageously, Y is an anionic counterion as defined previously.

The compounds of formula (I) or (II) may also be in the form of solvates, for example a hydrate or a solvate of a linear or branched alcohol such as ethanol or isopropanol.

Preferably, the 2- or 4-azopyridinium dye(s) are chosen from the following compounds, the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof:

Y being as defined previously.

More preferentially, the 2- or 4-azopyridinium dye(s) are chosen from the following compounds, the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof:

According to a particular embodiment, the dye(s) (a) are chosen from the 2-azopyridinium compounds of formula (II) as defined above. More preferentially, the dye(s) (a) are chosen from compounds (1) to (20).

According to another particular embodiment, the dye(s) (a) are chosen from the 4-azopyridinium compounds of formula (I) as defined above. According to this embodiment, the dye(s) (a) are preferably chosen from compounds (21) to (27), more preferentially (21a)-(27a), and better still the dye(s) (a) are chosen from compounds (21b), (23b), (26a) and (27a).

(b) Fluorescent Dyes

The process for dyeing keratin fibres and the composition according to the present invention also use, or comprise, (b) one or more fluorescent dyes.

Preferably the fluorescent dye(s) of the invention are direct dyes. More particularly, the fluorescent dye(s) of the invention are other than fluorescent dyes comprising a disulfide bond. More preferentially, the fluorescent dye(s) of the invention are direct dyes and do not comprise a bond containing contiguous identical heteroatoms.

As fluorescent dyes that may be used in the present invention, mention may be made of the following dyes: acridines, acridones, azlactones, benzanthrones, benzimidazoles, benzimidazolones, benzindoles, benzoxazoles, benzopyrans, benzothiazoles, coumarins, difluoro {2-[(2H-pyrrol-2-ylidene-kN)methyl]-1H-pyrrolato-kN}borons (BODIPY®), dipyrinones, diketopyrrolopyrroles, fluorindines, (poly)methines (especially cyanins and styryls/hemicyanins), naphthalimides, naphthanilides, naphthylamine (such as dansyls), naphtholactams, oxadiazoles, oxazines, perilones, perinones, perylenes, polyenes/carotenoids, squaranes, stilbenes, xanthenes, thioxanthenes, thiazines, and mixtures thereof.

Mention may also be made of the fluorescent dyes described in EP 1 133 975, WO 03/029 359, EP 860 636, WO 95/01772, WO 95/15144, EP 714 954 and those listed in the encyclopaedia The chemistry of synthetic dyes by K. Venkataraman, 1952, Academic Press, vol. 1 to 7, in Kirk Othmer's encyclopaedia Chemical Technology, in the chapter “Dyes and Dye Intermediates”, 1993, Wiley and Sons, and in various chapters of Ullmann's Encyclopedia of Industrial Chemistry, 7th edition, Wiley and Sons, especially in Ullmann's Encyclopedia of Industrial Chemistry in the chapter “Fluorescent Dyes”, 2005, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 10.1002/143560007.all 279; in The Handbook—A Guide to Fluorescent Probes and Labeling Technologies, 10th Ed Molecular Probes/Invitrogen—Oregon 2005 circulated by Internet or in the preceding printed editions.

Preferably, the fluorescent dye(s) (b) of the invention are chosen from coumarin dyes, (poly)methine dyes, in particular cyanin and styryl/hemicyanin dyes, and naphthalimide dyes.

More particularly, the fluorescent dye(s) of the invention are cationic.

Preferably, the fluorescent dye(s) of the invention are direct dyes chosen from (poly)methine dyes, in particular cyanin dyes and styryl/hemicyanin dyes, and naphthalimide dyes, and mixtures thereof; more preferentially, the fluorescent dyes are direct and cationic; and better still, the fluorescent dye(s) (b) are chosen from styryl or hemicyanin cationic dyes.

Better still, the fluorescent dyes of the invention absorb light in the yellow, orange and red range, preferably in the absorption wavelength λ_(abs) between 400 nm and 500 nm inclusive.

According to one variant, the fluorescent dyes of the invention contain at least one cationic radical borne by, or included in, at least one of the fluorescent chromophores.

Preferably, the cationic radical is a quaternary ammonium; better still, the cationic charge is endocyclic.

These cationic radicals are, for example, a cationic radical:

-   -   bearing an exocyclic (di/tri)(C₁-C₈)alkylammonium charge, or     -   bearing an endocyclic charge, such as the following cationic         heteroaryl groups: acridinium, benzimidazolium,         benzobistriazolium, benzopyrazolium, benzopyridazinium,         benzoquinolium, benzothiazolium, benzotriazolium, benzoxazolium,         bipyridinium, bis-tetrazolium, dihydrothiazolium,         imidazopyridinium, imidazolium, indolium, isoquinolium,         naphthoimidazolium, naphthoxazolium, naphthopyrazolium,         oxadiazolium, oxazolium, oxazolopyridinium, oxonium,         phenazinium, phenoxazolium, pyrazinium, pyrazolium,         pyrazoyltriazolium, pyridinium, pyridinoimidazolium, pyrrolium,         pyrylium, quinolium, tetrazolium, thiadiazolium, thiazolium,         thiazolopyridinium, thiazoylimidazolium, thiopyrylium,         triazolium or xanthylium.

According to a preferred variant of the invention, the fluorescent dyes of the invention bear at least one cationic chromophore and comprise at least one quaternary ammonium radical such as polymethine chromophores chosen from formulae (III) and (IV) below: W⁺—[C(R^(c))═C(R^(d))]_(m′)—Ar′—(*)Q⁻  (III) Ar—[C(R^(d))═C(R^(c))]_(m′)—W′⁺—(*)Q⁻  (IV), in which formulae (III) and (IV):

-   -   W⁺ represents a cationic heteroaryl group, in particular         comprising a quaternary ammonium optionally substituted with one         or more (C₁-C₈)alkyl groups optionally substituted in particular         with one or more hydroxyl groups;     -   W′⁺ represents a divalent heteroaryl radical as defined for W⁺;     -   Ar represents an aryl group such as phenyl or naphthyl,         optionally substituted preferably with i) one or more halogen         atoms such as chlorine or fluorine; ii) one or more (C₁-C₈)alkyl         and preferably C₁-C₄ alkyl groups such as methyl; iii) one or         more hydroxyl groups; iv) one or more (C₁-C₈)alkoxy groups such         as methoxy; v) one or more hydroxy(C₁-C₈)alkyl groups such as         hydroxyethyl, vi) one or more amino or (di)(C₁-C₈)alkylamino         groups, preferably with the C₁-C₄ alkyl part optionally         substituted with one or more hydroxyl groups, such as         (di)hydroxyethylamino, vii) with one or more acylamino         groups; viii) one or more heterocycloalkyl groups such as         piperazinyl, piperidyl or 5- or 6-membered heteroaryl such as         pyrrolidinyl, pyridyl and imidazolinyl;     -   Ar′ is a divalent aryl radical as defined for Ar;     -   m′ represents an integer between 1 and 4 inclusive, in         particular, m′ is 1 or 2; better still 1;     -   R^(c) and R^(d), which may be identical or different, represent         a hydrogen atom or optionally a substituted (C₁-C₈)alkyl and         preferably C₁-C₄ alkyl group, or alternatively R^(c) is         contiguous with W or W′ and/or R^(d) is contiguous with Ar or         Ar′ and form, with the atoms that bear them, a         (hetero)cycloalkyl; in particular, R^(c) is contiguous with W⁺         or W′⁺ and forms a (hetero)cycloalkyl such as cyclohexyl;     -   Q⁻ is an organic or mineral anionic counterion;     -   (*) represents the part of the fluorescent chromophore that is         bonded to the rest of the dye.

Preferably, W⁺ or W′⁺ is an imidazolium, pyridinium, benzimidazolium, pyrazolium, benzothiazolium or quinolinium radical optionally substituted with one or more identical or different C₁-C₄ alkyl radicals.

According to a particularly preferred embodiment of the invention, the fluorescent chromophore(s) of the dye (III) or (IV) are those defined previously with m′=1, Ar representing a phenyl group substituted para to the styryl group

—C(R^(d))═C(R^(c))— with a (di)(hydroxy)(C₁-C₆)(alkyl)amino group such as dihydroxy(C₁-C₄)alkylamino, and W′⁺ representing an imidazolium or pyridinium group, preferentially ortho- or para-pyridinium.

According to another preferred variant of the invention, the fluorescent chromophore(s) of the dyes are cationic and comprise at least one quaternary ammonium radical such as a naphthimidyl bearing a cationic exocyclic charge of formula (IIIa) or (IVa):

in which formulae (IIIa) and (IVa) R^(e), R^(f), R^(g) and R^(h), which may be identical or different, represent a hydrogen atom or a (C₁-C₆)alkyl group which is optionally substituted, preferentially with a di(C₁-C₆)alkylamino or tri(C₁-C₆)alkylammonium group such as trimethylammonium.

According to a particular embodiment, the fluorescent dye(s) of the invention (b) are chosen from those of formula (V), (VI) or (VII) below, and also the organic or mineral, acid or base salts thereof, the optical isomers, geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates:

in which formulae (V), (VI) and (VII):

-   -   R₁ and R₂, which may be identical or different, represent a         hydrogen atom or a C₁-C₆ alkyl group; preferentially a hydrogen         atom;     -   G₁ represents a hydrogen atom or a group chosen from NH₂ and OH;     -   R_(a), R′_(a), R″_(a), R″′_(a), R_(b), R′_(b), R″_(b) and         R′″_(b), which may be identical or different, represent a) a         hydrogen atom, b) a halogen atom, a group from among: c)         amino, d) (C₁-C₄)alkylamino, e) (C₁-C₄)dialkylamino, f)         cyano, g) carboxyl —C(O)OH or carboxylate —C(O)O⁻, Q⁺, h)         hydroxyl —OH or alkoxide —O⁻Q⁺, i) (poly)halo(C₁-C₆)alkyl such         as trifluoromethyl, j) acylamino, k) (C₁-C₆)alkoxy, 1)         (C₁-C₆)alkylthio, m) (poly)hydroxy(C₂-C₄)alkoxy, n)         (C₁-C₆)alkylcarbonyloxy, o) (C₁-C₆)alkoxycarbonyl, p)         (C₁-C₆)alkylcarbonylamino, q) acylamino, r) carbamoyl, s)         (C₁-C₆)alkylsulfonylamino, t) aminosulfonyl, u) —SO₃H or         sulfonate —SO₃ ⁻, Q⁺ or v) (C₁-C₆)alkyl optionally substituted         with a group chosen from (C₁-C₆)alkoxy, hydroxyl, cyano,         carboxyl, amino, (di)(C₁-C₄)alkylamino, or alternatively the two         alkyl radicals borne by the nitrogen atom of the amino group         form a 5- to 7-membered heterocycle optionally comprising         another nitrogen or non-nitrogen heteroatom; in particular,         R_(a), R′_(a), R″_(a), R″′_(a), R_(b), R′_(b), R″_(b) and         R″′_(b) represent a hydrogen or halogen atom or a (C₁-C₄)alkyl         group, preferably a hydrogen atom;     -   or alternatively two groups R_(a) and R′_(a); R_(b), and R′_(b)         borne by two adjacent carbon atoms together form a benzo or         indeno ring, a fused heterocycloalkyl or fused heteroaryl group;         the benzo, indeno, heterocycloalkyl or heteroaryl ring being         optionally substituted with a halogen atom, an amino,         (C₁-C₄)alkylamino, (C₁-C₄)dialkylamino, nitro, cyano, carboxyl,         hydroxyl or trifluoromethyl group, an acylamino, (C₁-C₄)alkoxy,         (poly)hydroxy(C₁-C₄)alkoxy, (C₁-C₄)alkylcarbonyloxy,         (C₁-C₄)alkoxycarbonyl or (C₁-C₄)alkylcarbonylamino radical, an         acylamino, carbamoyl or alkoxyalkylsulfonylamino radical, an         aminosulfonyl radical, or a (C₁-C₆)alkyl radical optionally         substituted with: a group chosen from (C₁-C₆)alkoxy, hydroxyl,         cyano, carboxyl, amino, (C₁-C₄)alkylamino and         (C₁-C₄)dialkylamino, or alternatively the two alkyl radicals         borne by the nitrogen atom of the amino group form a 5- to         7-membered heterocycle optionally comprising another nitrogen or         non-nitrogen heteroatom; preferentially, R_(a) and R′_(a)         together form a benzo group;     -   or alternatively, two groups R_(i) and R_(a); and/or a group         R′_(i) and R′_(a) together form a fused (hetero)cycloalkyl,         preferentially cycloalkyl such as cyclohexyl;     -   R_(g) represents a hydrogen atom, a (hetero)aryl(C₁-C₄)alkyl         group or a (C₁-C₆)alkyl group that is optionally substituted;         preferentially, R_(b) represents a hydrogen atom or a         (C₁-C₃)alkyl or benzyl group;     -   R_(e) represents a covalent bond, a linear or branched,         optionally substituted (C₁-C₆)alkylene or (C₂-C₈)alkenylene         hydrocarbon-based chain, preferably R_(e) represents an         unsubstituted (C₁-C₆)alkylene;     -   R_(f) represents a hydrogen atom, a (C₁-C₄)alkoxy group, an         amino group R₃R₄N—, a quaternary ammonium group M′, R₃R₄R₅N⁺— in         which R₃, R₄ and R₅, which may be identical or different,         represent a (C₁-C₄)alkyl group or R₃R₄N-represents an optionally         substituted heteroaryl group, preferentially an optionally         substituted imidazolyl group, or alternatively M′, R₃R₄R₅N⁺—         represents an optionally substituted cationic heteroaryl group,         preferentially an imidazolinium group optionally substituted         with a (C₁-C₃)alkyl group;     -   G represents i) a group —NR_(c)R_(d), ii) —OR with R         representing a) a hydrogen atom, b) an optionally substituted,         preferentially unsubstituted (C₁-C₆)alkyl group, c) an         optionally substituted (hetero)aryl group, d) an optionally         substituted (hetero)aryl(C₁-C₆)alkyl group such as benzyl, e)         optionally substituted (hetero)cycloalkyl, f) optionally         substituted (hetero)cycloalkyl(C₁-C₆)alkyl; according to a         particular embodiment, G represents a group —NR_(c)R_(d),         according to another particular embodiment, G represents a         (C₁-C₆)alkoxy group;     -   or alternatively when G represents —NR_(c)R_(d), two groups R,         and R′_(a) and/or R_(d) and R_(a) together form a saturated         heteroaryl or heterocycle, optionally substituted with one or         more (C₁-C₆)alkyl groups, preferentially a 5- to 7-membered         heterocycle containing one or two heteroatoms chosen from         nitrogen and oxygen; more preferentially, the heterocycle is         chosen from morpholinyl, piperazinyl, piperidyl and pyrrolidinyl         groups;     -   R_(c) and R_(d), which may be identical or different, represent         a hydrogen atom or a group from among: a) optionally substituted         (hetero)aryl such as phenyl, b) optionally substituted         (hetero)aryl(C₁-C₄)alkyl, c) optionally substituted         (hetero)cycloalkyl, d) optionally substituted         (hetero)cycloalkyl(C₁-C₄)alkyl, f) (C₂-C₅)alkyl or g)         (C₁-C₈)alkyl which is optionally substituted, preferably         optionally substituted with a hydroxyl, carboxyl, carboxylate,         sulfate or sulfonate group;

or alternatively two adjacent radicals R_(c) and R_(d) borne by the same nitrogen atom together form an optionally substituted heterocyclic or optionally substituted heteroaryl group;

-   -   R_(i) and R′_(i), which may be identical or different, represent         a hydrogen atom or a (C₁-C₄)alkyl group;

represents a (hetero)aryl group fused to the phenyl ring; or alternatively is absent from the phenyl; preferentially, when the ring is present, the ring is a benzo;

-   -   m represents an integer between 1 and 18 inclusive, particularly         an integer between 1 and 14 inclusive; preferentially an integer         between 2 and 10 inclusive; more preferentially an integer         between 3 and 8; more particularly an integer between 4 and 6;     -   M′ represents an anionic counterion, derived from a salt of an         organic or mineral acid, or from an organic or mineral base that         ensures the electrical neutrality of the dye;     -   Q represents a cationic counterion, derived from a salt of an         organic or mineral acid, or from an organic or mineral base that         ensures the electrical neutrality of the dye such as alkali         metal, alkaline-earth metal or ammonium;         it being understood that when the dye comprises a carboxylate,         sulfonate or alkoxide group, then M′ and Q⁺ may be absent to         ensure the electrical neutrality of said dye.

According to one embodiment, the fluorescent dyes of the invention are of formula (V) as defined previously.

According to a preferred embodiment, the fluorescent dye(s) of the invention are chosen from the styryl dyes of formula (VIII) below, and also the organic or mineral, acid or base salts thereof, the optical isomers, geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates:

in which formula (VIII) G, G₁, R_(a), R′_(a), R″_(a), R_(b), R′_(b), R″_(b), R_(i), R′_(i), R₁, R₂ and m are as defined previously for (V).

In particular, the dye(s) of the invention are chosen from those of formula (VIII) for which:

-   -   R₁ and R₂, which may be identical or different, represent a         hydrogen atom;     -   R_(i) and R_(i′), which may be identical or different, represent         a hydrogen atom or a (C₁-C₄)alkyl group, preferably hydrogen;     -   R_(a), R′_(a) and R″_(a), which may be identical or different,         represent a hydrogen atom, a halogen atom such as fluorine, or         an —OH, —O⁻Q⁺, (C₁-C₆)alkoxy, nitro, or cyano group, with Q⁺ as         defined previously;     -   R_(b), R′_(b) and R″_(b), which may be identical or different,         represent a hydrogen atom or a (C₁-C₆)alkyl group;     -   or alternatively two contiguous radicals R_(b) and R′_(b) form,         together with the carbon atoms that bear them, a benzo group         that is condensed or fused to the pyridinium group, said benzo         group possibly being substituted; preferably, said benzo group         is unsubstituted;     -   G represents a group —NR_(c)R_(d) or (C₁-C₆)alkoxy group which         is optionally substituted, preferentially unsubstituted;         according to a particular embodiment, G represents a group         —NR_(c)R_(d), according to another particular embodiment, G         represents a (C₁-C₆)alkoxy group;     -   R_(i) and R′_(i), which may be identical or different, represent         a hydrogen atom or a (C₁-C₄)alkyl group;

represents an aryl or heteroaryl group fused to the phenyl ring; or alternatively is absent from the phenyl ring; preferentially, when the ring is present, the ring is a benzo;

-   -   m represents an integer between 1 and 18 inclusive; particularly         an integer between 2 and 16 inclusive; preferentially an integer         between 3 and 10; more preferentially an integer between 4 and         6;     -   R_(c) and R_(d), which may be identical or different, represent         a hydrogen atom, a (C₂-C₄)alkyl group or a substituted         (C₁-C₈)alkyl group, preferably (C₂-C₄)alkyl substituted in         particular with one or more groups chosen from i) cyano, ii)         (C₁-C₃)alkoxy, iii) hydroxyl and iv) (C₁-C₃)alkylcarbonyl,         preferably with one or more hydroxyl groups; and     -   M′ representing an anionic counterion, derived from a salt of an         organic or mineral acid, or from an organic or mineral base that         ensures the electrical neutrality of the dye;         it being understood that when the dye comprises an alkoxide         group, then M′ and Q⁺ may be absent to ensure the electrical         neutrality of said dye.

Preferably, the fluorescent dye(s) (b) of the invention are chosen from the styryl dyes of formula (IX) below, and also the organic or mineral, acid or base salts thereof, the optical isomers, geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates:

in which formula (IX) G, G₁, R_(a), R′_(a), R_(b), R′_(b) and m are as defined previously.

According to a particular embodiment, the group G is in the para position relative to the —CH═CH— group, i.e. in position 4′ of the phenyl group. According to another particular embodiment of the invention, the group G is in the ortho position relative to the —CH═CH— group, i.e. in position 2′ of the phenyl group. According to one embodiment, the —CH═CH— group is in the para position relative to the pyridinium group, i.e. in position 4.

According to another advantageous variant, the —CH═CH— group is in the ortho position relative to the pyridinium group, i.e. in position 2.

According to a preferred mode of the invention, the fluorescent dye(s) (b) of the invention are chosen from the compounds of formulae (X) and (XI) below, and also the organic or mineral, acid or base salts thereof, the optical isomers, geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates:

in which formulae (X) and (XI):

-   -   R¹, R², R³ and R⁴, which may be identical or different,         represent a hydrogen atom or a (C₁-C₆)alkyl group; preferably,         R² and R³ represent a hydrogen atom and R¹ and R⁴, which may be         identical or different, represent a hydrogen atom or a         (C₁-C₄)alkyl group;     -   R⁵, R⁶, R⁷, R⁸ and R⁹, which may be identical or different,         represent i) a hydrogen atom or ii) a halogen atom such as Cl,         Br or F, iii) a group OR in which R represents a hydrogen atom         or Q⁺ as described previously, or a (C₁-C₃)alkyl group, a group         from among iv) aryl such as benzene, v) aryl(C₁-C₃)alkyl such as         benzyl, vi) cyano, vii) nitro, viii) (C₁-C₃)alkylthio, ix) amino         NR⁰R¹¹ with R¹⁰ and R¹¹, which may be identical or different,         representing a) a hydrogen atom, b) a (C₂-C₄)alkyl group or c) a         substituted (C₁-C₅)alkyl group, preferably (C₂-C₄)alkyl group         optionally substituted with one or more groups chosen from:         -   cyano,         -   (C₁-C₃)alkoxy,         -   hydroxyl, and         -   (C₁-C₃)alkylcarbonyl;         -   in particular, R¹⁰ and R¹¹, which may be identical or             different, represent a hydrogen atom or a (C₁-C₆)alkyl group             substituted with one or more hydroxyl, cyano or             (C₁-C₃)alkylcarbonyl groups such as hydroxyethyl;     -   m represents an integer between 1 and 18 inclusive; particularly         an integer between 2 and 16 inclusive; preferentially an integer         between 3 and 10; more preferentially an integer between 4 and         6;     -   M′ represents an anionic counterion as defined previously;         it being understood that when the dye comprises an alkoxide         group, then M′ and Q may be absent to ensure the electrical         neutrality of said dye.

According to a first embodiment of the invention, the fluorescent dye(s) (b) are of formula (X) with:

R¹ R² R³ R⁴ R⁵ R⁶ R⁷ R⁸ R⁹ m H H H H H H H H H 1 H H H H H t-Bu OH t-Bu H 5 H H H H H t-Bu OH t-Bu H 5 H H H H H H NH₂ H H 1 H H H H H H NH₂ H OCH₃ 1 H H H H H H OH Br H 5 H H H H H OCH₃ OH OCH₃ H 5 H H H H Cl H OH H Cl 5 H H H H H H OH H H 10 H H H H H OCH₃ OH OCH₃ H 10 H H H H H t-Bu OH t-Bu H 10 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H t-Bu OH t-Bu H 10 H H H H H H N(CH₂CH₃)CH₂CH₂OH H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H n-C₆H₁₃ H H 1 H H H H H H N(CH₂CH₂OH)₂ H H 2 H H H H H H N(n-Bu)₂ H H 2 H H H H H OCH₃ OH H H 10 H H H H H H OC₂H₅OH H H 1 H H H H H H OH H H 1 H H benzo H H H H H 1 H H benzo H H N(CH₂CH₂OH)₂ H H 1 H H benzo H H N(CH₂CH₂OH)₂ H H 1 and also the organic or mineral, acid or base salts thereof, the optical isomers, geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates.

According to a second embodiment, the fluorescent dye(s) (b) are of formula (XI) with:

R¹ R² R³ R⁴ R⁵ R⁶ R⁷ R⁸ R⁹ m CH₃ H H H OH H OCH₃ H H 2 CH₃ H H H H H OCH₃ OCH₂—Ph H 2 CH₃ H H H H H H H OCH₃ 2 CH₃ H H H F H H H H 2 CH₃ H H H H H H OPh H 2 CH₃ H H H H H N(CH₂CH₂OAc)₂ H H 2 CH₃ H H H OCH₃ H OCH₃ OCH₃ H 2 CH₃ H H H H H H CH₃ H 2 CH₃ H H H H H OH H H 2 CH₃ H H H H OCH₃ OCH₃ OCH₃ H 2 CH₃ H H H H OCH₃ OH OH H 2 CH₃ H H H H H OCH₃ OCH₃ OCH₃ 2 CH₃ H H H H H H OCH₃ OH 2 CH₃ H H H H H N(n-butyl)₂ H H 2 CH₃ H H H H OCH₃ OCH₃ H H 2 CH₃ H H H H H H H H 2 CH₃ H H H H H i-propyl H H 2 H H H H H H OH H H 6 H H H H H OCH₃ OCH₃ OCH₃ H 6 H H H H OH H OCH₃ H H 2 H H H H OCH₃ H H OCH₃ OCH₃ 2 H H H H H H H H Br 2 H H H H H H OH H H 2 H H H H OCH₃ OCH₃ OCH₃ H H 6 H H H H OH OCH₃ H H H 6 H H H H H OCH₃ OCH₃ H H 6 H H H H H OCH₃ OCH₃ H H 2 H H H H H H C(O)—OH H H 6 H H H H H H C(O)—OH H H 2 H H H H H H i-propyl H H 2 H H H H H H N(CH₃)CH₂CH₂CN H H 2 H H H H H H OCH₃ OCH₂Ph H 2 H H H H H H H OPh H 2 H H H H H H N(CH₂CH₂C(O)CH₃)₂ H H 2 H H H H OH H OCH₃ H H 6 H H H H H OCH₃ OCH₃ OCH₃ H 2 H H H H OCH₃ H OCH₃ OCH₃ H 6 H H H H H H H CH₃ H 2 H H H H H H N(CH₃)CH₂CH₂OH H H 2 and also the organic or mineral, acid or base salts thereof, the geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates.

Preferably, the fluorescent dye(s) (b) are chosen from those of formulae (X′) and (XI′) below:

in which formulae (X′) and (XI′) R⁵, R⁷, R⁸ and m are as defined previously for (X) and (XI), in particular:

-   -   R⁵ and R⁸, which may be identical or different, represent a         hydrogen atom or a (C₁-C₄)alkoxy group such as methoxy;     -   R⁷ represents a (C₁-C₄)alkoxy group or NR¹⁰R¹¹ with R¹⁰         representing a) a hydrogen atom, or b) a (C₁-C₆)alkyl group         optionally substituted with one or more groups chosen from i)         cyano, ii) (C₁-C₃)alkoxy, iii) hydroxyl and iv)         (C₁-C₃)alkylcarbonyl and R¹¹ representing a) a (C₂-C₅)alkyl         group substituted with one or more groups chosen from i)         cyano, ii) (C₁-C₃)alkoxy, iii) hydroxyl and iv)         (C₁-C₃)alkylcarbonyl;     -   in particular, NR¹⁰R¹¹ represents a (C₂-C₄)alkyl group, a         (di)hydroxy(C₂-C₄)alkylamino or         hydroxy(C₂-C₄)alkyl((C₁-C₄)alkyl)amino group;     -   m represents an integer between 1 and 18 inclusive; particularly         an integer between 2 and 16 inclusive; preferentially an integer         between 3 and 10; more preferentially an integer between 4 and         6; and     -   M′ represents an anionic counterion, derived from a salt of an         organic or mineral acid, or from an organic or mineral base that         ensures the electrical neutrality of the dye.

According to this embodiment, the fluorescent dye(s) (b) are preferably chosen from those of formula (X′) or (XI′) with:

R⁵ R⁷ R⁸ m R⁵ R⁷ R⁸ m H N(CH₂CH₂OH)₂ H 2 and OCH₃ OCH₃ OCH₃ 2 H N(CH₂CH₂OH)₂ H 3 OCH₃ OCH₃ OCH₃ 3 H N(CH₂CH₂OH)₂ H 4 OCH₃ OCH₃ OCH₃ 3 H N(CH₂CH₂OH)₂ H 5 OCH₃ OCH₃ OCH₃ 4 H N(CH₂CH₂OH)₂ H 6 OCH₃ OCH₃ OCH₃ 5 H N(CH₂CH₂OH)₂ H 8 OCH₃ OCH₃ OCH₃ 8 H N(CH₂CH₂OH)₂ H 10 OCH₃ OCH₃ OCH₃ 10 H N(CH₂CH₂OH)₂ H 12 OCH₃ OCH₃ OCH₃ 12 H N(CH₂CH₂OH)₂ H 14 OCH₃ OCH₃ OCH₃ 14 H N(CH₂CH₂OH)₂ H 16 OCH₃ OCH₃ OCH₃ 16 H CH₃CH₂N(CH₂CH₂OH) H 2 H CH₃CH₂N(CH₂CH₂OH) H 4 and also the organic or mineral, acid or base salts thereof, the geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates.

According to yet another preferred mode of the invention, the fluorescent dye(s) (b) of the invention are chosen from the compounds of formulae (XII) and (XIII) below, and also the organic or mineral, acid or base salts thereof, the optical isomers, geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates:

in which formulae (XII) and (XIII):

-   -   R¹, R², R³ and R⁴, which may be identical or different,         represent a hydrogen atom or a (C₁-C₆)alkyl group; preferably,         R² and R³ represent a hydrogen atom and R¹ and R⁴, which may be         identical or different, represent a hydrogen atom or a         (C₁-C₄)alkyl group;     -   R⁵, R⁶, R⁷, R⁸ and R⁹, which may be identical or different,         represent i) a hydrogen atom or ii) a halogen atom such as Cl,         Br or F, iii) a group OR in which R represents a hydrogen atom         or Q as described previously, or a (C₁-C₃)alkyl group, a group         from among iv) aryl such as benzene, v) aryl(C₁-C₃)alkyl such as         benzyl, vi) cyano, vii) nitro, viii) (C₁-C₃)alkylthio, ix) amino         NR¹⁰R¹¹ with R¹⁰ and R¹¹, which may be identical or different,         representing a) a hydrogen atom or b) a (C₁-C₈)alkyl group         optionally substituted with one or more groups chosen from:         -   cyano,         -   (C₁-C₃)alkoxy,         -   hydroxyl, and         -   (C₁-C₃)alkylcarbonyl;         -   in particular, R¹⁰ and R¹¹, which may be identical or             different, represent a hydrogen atom or a (C₁-C₆)alkyl group             optionally substituted with one or more hydroxyl, cyano or             (C₁-C₃)alkylcarbonyl groups such as methyl, ethyl, butyl,             isobutyl, cyanoethyl, methylcarbonylethyl, or hydroxyethyl;     -   m represents an integer between 1 and 18 inclusive; particularly         an integer between 2 and 16 inclusive; preferentially an integer         between 3 and 10; more preferentially an integer between 4 and         6;     -   M′ represents an anionic counterion derived from salts of         organic or mineral acids preferably originating from Y;         it being understood that when the dye comprises an alkoxide         group, then M′ and Q⁺ may be absent to ensure the electrical         neutrality of said dye.

According to one embodiment of the invention, the fluorescent dye(s) (b) are of formula (XII) with:

R¹ R² R³ R⁴ R⁵ R⁶ R⁷ R⁸ R⁹ m H H H H H H OCH₃ OCH₃ OCH₃ 2 H H H H OH OCH₃ H H H 2 H H H H H H H H H 2 H H H H H OCH₃ OCH₃ H H 2 H H H H OH H OH H H 6 H H H H OCH₃ H OCH₃ OCH₃ H 6 H H H H H H OH H H 6 H H H H OCH₃ H H H F 2 H H H H H H C(O)—OH H H 2 H H H H H H Isopropyl H H 2 H H H H H H N(CH₂CH₂C(O)CH₃)₂ H H 2 H H H H OH H OCH₃ H H 2 H H H H H H OH H H 2 H H H H H OCH₃ OH OH H 2 H H H H H CH₃ OCH₂Ph CH₃ H 2 H H H H H OCH₃ OCH₃ OCH₃ H 2 H H H H H OCH₃ OCH₃ OCH₃ H 6 H H H H H H N(CH₃)₂ H H 6 H H H H H H OCH₃ OCH₃ OCH₃ 6 H H H H H H Phenyl H H 6 H H H H H OCH₃ OCH₃ H H 6 H H H H H H C(O)—OH H H 6 H H H H H H N(n-Butyl)₂ H H 2 H H H H H H OCH₃ OCH₃ H 3 H H H H H H OCH₃ OCH₃ H 2 H H H H H H OCH₃ OCH₃ H 5 H H H H H H OCH₃ H H 3 H H H H H H N(CH₃)₂ H H 3 H H H H H H H H H 3 and also the organic or mineral, acid or base salts thereof, the optical isomers, geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates.

According to another embodiment, the fluorescent dye(s) (b) are of formula (XIII) with:

R¹ R² R³ R⁴ R⁵ R⁶ R⁷ R⁸ R⁹ m CH₃ H H H OH H OCH₃ H H 2 CH₃ H H H H H OCH₃ OCH₂—Ph H 2 CH₃ H H H H H H H OCH₃ 2 CH₃ H H H F H H H H 2 CH₃ H H H H H H OPh H 2 CH₃ H H H H H N(CH₂CH₂OAc)₂ H H 2 CH₃ H H H OCH₃ H OCH₃ OCH₃ H 2 CH₃ H H H H H H CH₃ H 2 CH₃ H H H H H OH H H 2 CH₃ H H H H OCH₃ OCH₃ OCH₃ H 2 CH₃ H H H H OCH₃ OH OH H 2 CH₃ H H H H H OCH₃ OCH₃ OCH₃ 2 CH₃ H H H H H H OCH₃ OH 2 CH₃ H H H H H N(n-butyl)₂ H H 2 CH₃ H H H H OCH₃ OCH₃ H H 2 CH₃ H H H H H H H H 2 CH₃ H H H H H i-propyl H H 2 H H H H H H OH H H 6 H H H H H OCH₃ OCH₃ OCH₃ H 6 H H H H OH H OCH₃ H H 2 H H H H OCH₃ H H OCH₃ OCH₃ 2 H H H H H H H H Br 2 H H H H H H OH H H 2 H H H H H H N(CH₃)₂ H H 6 H H H H OCH₃ OCH₃ OCH₃ H H 6 H H H H OH OCH₃ H H H 6 H H H H H OCH₃ OCH₃ H H 6 H H H H H OCH₃ OCH₃ H H 2 H H H H H H C(O)—OH H H 6 H H H H H H C(O)—OH H H 2 H H H H H H i-propyl H H 2 H H H H H H N(CH₃)CH₂CH₂CN H H 2 H H H H H H OCH₃ OCH₂Ph H 2 H H H H H H H OPh H 2 H H H H H H N(CH₂CH₂C(O)CH₃)₂ H H 2 H H H H OH H OCH₃ H H 6 H H H H H OCH₃ OCH₃ OCH₃ H 2 H H H H OCH₃ H OCH₃ OCH₃ H 6 H H H H H H H CH₃ H 2 H H H H H H N(CH₃)CH₂CH₂OH H H 2 CH₃ H H H H H N(CH₃)₂ H H 2 and also the organic or mineral, acid or base salts thereof, the geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates.

More particularly, the fluorescent dyes (b) of the invention are chosen from those of formulae (XII′) and (XIII′) below:

in which formulae (XII′) and (XIII′) R⁵, R⁷, R⁸ and m are as defined previously for (X) and (XI), in particular:

-   -   R⁵ and R⁸, which may be identical or different, represent a         hydrogen atom or a (C₁-C₄)alkoxy group such as methoxy;     -   R⁷ represents a (C₁-C₄)alkoxy group or NR¹⁰R¹¹ with R¹⁰ and R¹¹,         which may be identical or different, representing a) a hydrogen         atom, or b) a (C₁-C₈)alkyl group optionally substituted with one         or more groups chosen from i) cyano, ii) (C₁-C₃)alkoxy, iii)         hydroxyl, and iv) (C₁-C₃)alkylcarbonyl; in particular, R¹⁰ and         R¹¹, which may be identical or different, represent a hydrogen         atom or a (C₁-C₆)alkyl group optionally substituted with one or         more groups from the following: hydroxyl, cyano or         (C₁-C₃)alkylcarbonyl such as methyl, ethyl, butyl, isobutyl,         cyanoethyl, methylcarbonylethyl or hydroxyethyl; preferably, R¹⁰         and R¹¹, which may be identical or different, represent a         (C₁-C₆)alkyl group optionally substituted with one or more         hydroxyl groups such as hydroxyethyl;     -   m represents an integer between 1 and 18 inclusive; particularly         an integer between 2 and 16 inclusive; preferentially an integer         between 3 and 10; more preferentially an integer between 4 and         6; and     -   M′ represents an anionic counterion, derived from a salt of an         organic or mineral acid, or from an organic or mineral base that         ensures the electrical neutrality of the dye.

According to one embodiment, the fluorescent dye(s) (b) of the invention are of formula (XII′) or (XIII′) with:

R⁵ R⁷ R⁸ m R⁵ R⁷ R⁸ m H N(CH₂CH₂OH)₂ H 2 and OCH₃ OCH₃ OCH₃ 2 H N(CH₂CH₂OH)₂ H 3 OCH₃ OCH₃ OCH₃ 3 H N(CH₂CH₂OH)₂ H 4 OCH₃ OCH₃ OCH₃ 3 H N(CH₂CH₂OH)₂ H 5 OCH₃ OCH₃ OCH₃ 4 H N(CH₂CH₂OH)₂ H 6 OCH₃ OCH₃ OCH₃ 5 H N(CH₂CH₂OH)₂ H 8 OCH₃ OCH₃ OCH₃ 8 H N(CH₂CH₂OH)₂ H 10 OCH₃ OCH₃ OCH₃ 10 H N(CH₂CH₂OH)₂ H 12 OCH₃ OCH₃ OCH₃ 12 H N(CH₂CH₂OH)₂ H 14 OCH₃ OCH₃ OCH₃ 14 H N(CH₂CH₂OH)₂ H 16 OCH₃ OCH₃ OCH₃ 16 and also the organic or mineral, acid or base salts thereof, the geometrical isomers and tautomers thereof, and the solvates thereof such as hydrates.

More particularly, the fluorescent dye(s) (b) of the invention are chosen from those of formula (V), (VIII) or (IX) as defined previously in which G represents a hydrogen atom.

More particularly, the fluorescent dye(s) (b) of the invention are chosen from those of formulae (XIV) and (XV) below:

in which formulae (XIV) and (XV) R⁵, R⁷, R⁸ and m are as defined previously for (X) and (XI), in particular:

-   -   R⁵ and R⁸, which may be identical or different, represent a         hydrogen atom or a (C₁-C₄)alkoxy group such as methoxy,         preferably, R⁵ and R⁸ represent a hydrogen atom;     -   R⁷ represents a (C₁-C₄)alkoxy group or NR¹⁰R¹¹ with R¹⁰ and R¹¹,         which may be identical or different, representing a) a hydrogen         atom, or b) a (C₁-C₈)alkyl group optionally substituted with one         or more groups chosen from i) hydroxyl, ii) R—Z—C(X)—Y— with X,         Y and Z representing an oxygen or sulfur atom or N(R′), or         alternatively X and/or Z represent a bond, R and R′, which may         be identical or different, represent a hydrogen atom or a         (C₁-C₆)alkyl group, preferably, X represents an oxygen         atom, iii) sulfonic SO₃H, iv) sulfonate SO₃ ⁻, Q⁺, v)         carboxylate C(O)O⁻, Q⁺ with Q⁺ representing a cationic         counterion such as an alkali metal or alkaline-earth metal; in         particular, R⁷ represents a group NR¹⁰R¹¹ with R¹⁰ and R¹¹,         which may be identical or different, representing a) a hydrogen         atom, or b) a (C₁-C₆)alkyl group optionally substituted with one         or more groups chosen from i) hydroxyl, ii) carboxyl, iii)         carboxylate, iv) sulfonic, and v) sulfonate, more particularly         chosen from identical or different groups representing a) a         hydrogen atom, or b) a (C₁-C₆)alkyl group optionally substituted         with one or more groups chosen from i) hydroxyl, ii) carboxyl,         and iii) carboxylate;     -   m represents an integer between 1 and 18 inclusive; particularly         an integer between 1 and 6 inclusive; preferentially an integer         between 1 and 4; more preferentially an integer between 1 and 2;         and     -   M′ represents an anionic counterion, derived from a salt of an         organic or mineral acid, or from an organic or mineral base that         ensures the electrical neutrality of the dye;         it being understood that when the dye comprises a sulfonate or         carboxylate group, then M′ and Q may be absent to ensure the         electrical neutrality of said dye.

More preferentially, the fluorescent dye(s) (b) of the invention are chosen from the following compounds, and also the geometrical isomers thereof, the tautomers thereof, the solvates thereof and mixtures thereof:

with M′ and Q⁺ as defined previously.

The Oxidizing Agents

The process for dyeing keratin fibres and the cosmetic composition according to the present invention may also optionally use, or comprise, one or more oxidizing agents.

Preferably, the oxidizing agent(s) are chosen from chemical oxidizing agents.

The term “chemical oxidizing agent” means an oxidizing agent other than atmospheric oxygen.

More particularly, the chemical oxidizing agent(s) are chosen from hydrogen peroxide, hydrogen peroxide-generating systems, urea peroxide, alkali metal bromates or ferricyanides, peroxygenated salts, for instance persulfates, perborates, peracids and precursors thereof and percarbonates of alkali metals or alkaline-earth metals, and mixtures thereof.

Preferably, the chemical oxidizing agent(s) are chosen from hydrogen peroxide and hydrogen peroxide-generating systems.

According to a preferred embodiment, the hydrogen peroxide-generating system(s) are chosen from urea peroxide; polymeric complexes that can release hydrogen peroxide, chosen from polyvinylpyrrolidone/H₂O₂; oxidases; perborates; and percarbonates.

Preferably, the chemical oxidizing agent is hydrogen peroxide, and more preferentially aqueous hydrogen peroxide solution.

The chemical oxidizing agent(s) are advantageously applied in the form of an aqueous solution of which the content of chemical oxidizing agents is preferably between 0.05% and 5% by weight and more preferentially between 0.1% and 2% by weight, relative to the total weight of the aqueous solution.

According to a preferred embodiment of the invention, the dyeing process does not use any oxidizing agent.

According to this preferred embodiment of the invention, the cosmetic composition comprising ingredients (a) and (b) does not comprise any oxidizing agent.

The Reducing Agents

The process for dyeing keratin fibres and the cosmetic composition according to the present invention may also optionally use, or comprise, one or more reducing agents.

The reducing agent(s) that are useful in the present invention are advantageously chosen from the compounds of formula (XVI) below, and also the addition salts thereof and mixtures thereof: H(X)_(q)(R₁₀)_(t)  (XVI) in which formula (XVI):

-   -   X represents P, S or SO₂,     -   q represents an integer equal to 0 or 1,     -   t represents an integer equal to 1 or 2, and     -   R represents a linear or branched, saturated or unsaturated C₁         to C₂₀ alkyl radical, optionally interrupted with a heteroatom,         and/or optionally substituted with one or more radicals chosen         from hydroxyl, halo, amine, carboxyl, ((C₁-C₃₀)alkoxy)carbonyl,         amido, ((C₁-C₃₀)alkyl)aminocarbonyl, ((C₁-C₃₀)acyl)amino, mono-         or dialkylamino, and mono- or dihydroxylamino radicals.

Preferably, the reducing agent(s) are chosen from thioglycolic acid, thiolactic acid, glyceryl monothioglycolate, cysteamine, N-acetylcysteamine, N-propionylcysteamine, cysteine, N-acetylcysteine, thiomalic acid, pantetheine, 2,3-dimercaptosuccinic acid, N-(mercaptoalkyl)-ω-hydroxyalkylamides, N-mono- or N,N-dialkylmercapto-4-butyramides, aminomercaptoalkylamides, N-(mercaptoalkyl)succinamic acid and N-(mercaptoalkyl)succinimide derivatives, alkylamino mercaptoalkylamides, the azeotropic mixture of 2-hydroxypropyl thioglyconate and of (2-hydroxy-1-methyl)ethyl thioglycolate, mercaptoalkylaminoamides, N-mercaptoalkylalkanediamides and formamidinesulfinic acid derivatives, salts thereof, and mixtures thereof.

Preferably, the reducing agent(s) are also chosen from salts such as sodium sulfite, sodium dithionite or sodium thiosulfate, and mixtures thereof.

The chemical reducing agent(s) are advantageously applied in the form of an aqueous solution of which the content of chemical reducing agents is preferably between 0.01% and 10% by weight and more preferentially between 0.1% and 5% by weight, relative to the total weight of the aqueous solution.

According to a preferred embodiment of the invention, the dyeing process does not use any reducing agent.

According to this preferred embodiment of the invention, the cosmetic composition comprising ingredients (a) and (b) does not comprise any reducing agent.

The Cosmetic Medium and the Solvents

The 2- or 4-azopyridinium dye(s) (a) chosen from the compounds of formula (I) or (II), as defined previously, and (b) the fluorescent dye(s), as defined previously, and also, when they are present, the oxidizing agent(s) and/or the reducing agent(s), may be dissolved beforehand before being applied to the keratin fibres.

In other words, the ingredients used in the dyeing process of the present invention may be present in one or more compositions.

The composition(s) comprising the ingredients according to the present invention are cosmetic compositions, i.e. they are preferably aqueous. Besides water, they may comprise one or more organic solvents, or mixtures thereof.

Examples of organic solvents that may be mentioned include linear or branched C₂ to C₄ alkanols, such as ethanol and isopropanol; glycerol; polyols and polyol ethers, for instance 2-butoxyethanol, propylene glycol, hexylene glycol, dipropylene glycol, propylene glycol monomethyl ether, diethylene glycol monomethyl ether and monoethyl ether, and also aromatic alcohols or ethers, for instance benzyl alcohol or phenoxyethanol, and mixtures thereof.

The pH

The pH of the composition(s) used in the dyeing process of the invention and of the composition of the invention comprising ingredients (a) and (b) is preferably between 2 and 12 and more preferentially between 3 and 11. It may be adjusted to the desired value by means of acidifying or basifying agents usually used in the dyeing of keratin fibres, or alternatively using standard buffer systems.

The pH of the composition which comprises ingredients (a) and (b) and that of the composition(s) used in the dyeing process of the invention is preferably between 6 and 11 inclusive, more preferentially between 7 and 10 and better still between 7.5 and 9.5, such as between 9 and 9.5.

Among the acidifying agents as defined previously, mention may be made, by way of example, of mineral or organic acids, for instance hydrochloric acid, orthophosphoric acid or sulfuric acid, carboxylic acids, for instance acetic acid, tartaric acid, citric acid and lactic acid, and sulfonic acids.

The alkaline agent(s) may be chosen especially from mineral, organic or hybrid alkaline agents, and mixtures thereof.

The mineral alkaline agent(s) are preferably chosen from aqueous ammonia, alkaline carbonates or bicarbonates such as ammonium, sodium or potassium carbonate or bicarbonate, ammonium, sodium or potassium hydroxide, or mixtures thereof.

The organic alkaline agent(s) are preferably chosen from organic amines with a pK_(b) at 25° C. of less than 12, preferably of less than 10 and more advantageously still of less than 6. It should be noted that it concerns the pK_(b) corresponding to the function having the highest basicity. In addition, the organic amines do not comprise any alkyl or alkenyl fatty chain comprising more than ten carbon atoms.

The organic alkaline agent(s) are preferably chosen from alkanolamines, in particular mono-, di- or trihydroxy(C₁-C₆)alkylamines, such as triethanolamine, oxyethylenated and/or oxypropylenated ethylenediamines, amino acids, polyamines of formula (XVII) below, and mixtures thereof:

in which formula (XVII) W is a divalent C₁ to C₆ alkylene radical optionally substituted with one or more hydroxyl groups or a C₁ to C₆ alkyl radical, and/or optionally interrupted with one or more heteroatoms such as O, or NR_(u); R_(x), R_(y), R_(z), R_(t) and R_(u), which may be identical or different, represent a hydrogen atom or a C₁ to C₆ alkyl, C₁ to C₆ hydroxyalkyl or C₁ to C₆ aminoalkyl radical.

Examples of amines of formula (XVII) that may be mentioned include 1,3-diaminopropane, 1,3-diamino-2-propanol, spermine and spermidine.

The term “alkanolamine” means an organic amine comprising a primary, secondary or tertiary amine function, and one or more linear or branched C₁ to C₈ alkyl groups bearing one or more hydroxyl radicals.

Organic amines chosen from alkanolamines such as monoalkanolamines, dialkanolamines or trialkanolamines comprising one to three identical or different C₁ to C₄ hydroxyalkyl radicals are in particular suitable for use in the invention.

Among the compounds of this type, mention may be made of monoethanolamine (MEA), diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, N,N-dimethylethanolamine, 2-amino-2-methyl-1-propanol, triisopropanolamine, 2-amino-2-methyl-1,3-propanediol, 3-amino-1,2-propanedio 1,3-dimethylamino-1,2-propanediol and tris(hydroxymethyl)aminomethane.

More particularly, the amino acids that may be used are of natural or synthetic origin, in their L, D or racemic form, and comprise at least one acid function chosen more particularly from carboxylic acid, sulfonic acid, phosphonic acid and phosphoric acid functions. The amino acids may be in neutral or ionic form.

As amino acids that may be used in the present invention, mention may be made in particular of aspartic acid, glutamic acid, alanine, arginine, ornithine, citrulline, asparagine, carnitine, cysteine, glutamine, glycine, histidine, lysine, isoleucine, leucine, methionine, N-phenylalanine, proline, serine, taurine, threonine, tryptophan, tyrosine and valine.

Advantageously, the amino acids are basic amino acids comprising an additional amine function optionally included in a ring or in a ureido function.

Such basic amino acids are preferably chosen from those corresponding to formula (XVIII) below, and also salts thereof: R—CH₂—CH(NH₂)—C(O)—OH  (XVIII) in which formula (XVIII) R represents a group chosen from imidazolyl, preferably imidazolyl-4-yl; aminopropyl; aminoethyl; —(CH₂)₂N(H)—C(O)—NH₂; and —(CH₂)₂—N(H)—C(NH)—NH₂.

The compounds corresponding to formula (XVIII) are histidine, lysine, arginine, ornithine and citrulline.

The organic amine may also be chosen from organic amines of heterocyclic type. Besides histidine that has already been mentioned in the amino acids, mention may in particular be made of pyridine, piperidine, imidazole, triazole, tetrazole and benzimidazole.

The organic amine may also be chosen from amino acid dipeptides. As amino acid dipeptides that may be used in the present invention, mention may be made especially of carnosine, anserine and balenine.

The organic amine may also be chosen from compounds comprising a guanidine function. As amines of this type that may be used in the present invention, besides arginine, which has already been mentioned as an amino acid, mention may be made in particular of creatine, creatinine, 1,1-dimethylguanidine, 1,1-diethylguanidine, glycocyamine, metformin, agmatine, n-amidinoalanine, 3-guanidinopropionic acid, 4-guanidinobutyric acid and 2-([amino(imino)methyl]amino)ethane-1-sulfonic acid.

Hybrid compounds that may be mentioned include the salts of the amines mentioned previously with acids such as carbonic acid or hydrochloric acid.

Guanidine carbonate or monoethanolamine hydrochloride may be used in particular.

Preferably, the alkaline agent(s) that are useful in the invention are chosen from aqueous ammonia, alkaline carbonates or bicarbonates, alkanolamines, amino acids in neutral or ionic form, in particular basic amino acids, and preferably corresponding to those of formula (XVIII).

More preferentially, the alkaline agent(s) are chosen from aqueous ammonia, ammonium bicarbonate, ammonium hydroxide, mono-, di- or trihydroxy(C₁-C₆)alkylamines, such as triethanolamine, and mixtures thereof.

Forms of the Composition

The composition(s) comprising the 2- or 4-azopyridinium dye(s) (a) chosen from the compounds of formula (I) or (II) as defined previously, and the fluorescent dye(s) (b) as defined previously, may be in various presentation forms, such as in the form of liquids, lotions, creams or gels or in any other form that is suitable for dyeing keratin fibres.

It may also be packaged under pressure in an aerosol can in the presence of a propellant or in a non-aerosol can and may form a foam.

Additives

When the ingredients used in the dyeing process according to the present invention are present in one or more composition(s), said compositions may also optionally comprise one or more additives, different from the ingredients of the invention and among which mention may be made of fatty substances, cationic, anionic, nonionic, amphoteric or zwitterionic surfactants, cationic, anionic, nonionic or amphoteric polymers or mixtures thereof, antidandruff agents, anti-seborrhoea agents, agents for preventing hair loss and/or for promoting hair regrowth, vitamins and provitamins including panthenol, sunscreens, mineral or organic pigments, sequestrants, plasticizers, solubilizers, acidifying agents, mineral or organic thickeners, especially polymeric thickeners, opacifiers or nacreous agents, antioxidants, hydroxy acids, fragrances, preserving agents, pigments and ceramides.

Needless to say, a person skilled in the art will take care to select this or these optional additional compound(s) such that the advantageous properties intrinsically associated with the composition(s) in accordance with the invention are not, or are not substantially, adversely affected by the envisaged addition(s).

The above additives may generally be present in an amount, for each of them, of between 0 and 20% by weight relative to the total weight of the composition comprising them.

The Dyeing Process

The process for dyeing keratin fibres according to the present invention comprises the application to said keratin fibres of the following ingredients: (a) one or more 2- or 4-azopyridinium dyes chosen from the compounds of formula (I) or (II) as defined previously, and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof, and (b) one or more fluorescent dyes, as defined previously,

it being understood that the 2- or 4-azopyridinium dye(s) (a) (ingredients (a)) and the fluorescent dye(s) (ingredients (b)) are applied to said keratin fibres together or sequentially.

In other words, the dyeing process according to the present invention may be performed in one or more steps.

According to a particularly preferred embodiment, the 2- or 4-azopyridinium dye(s) (a) and the fluorescent dye(s) (b), as defined previously, are applied together (or jointly), i.e. simultaneously, to the keratin fibres. According to this embodiment, the dyeing process is performed in one step.

According to this one-step embodiment, the process comprises a step of applying to said keratin fibres a cosmetic composition according to the invention which comprises one or more 2- or 4-azopyridinium dyes (a) chosen from the compounds of formula (I) or (II) as defined previously, and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof, and one or more fluorescent dyes (b) as defined previously.

According to another particularly preferred embodiment, the 2- or 4-azopyridinium dye(s) (a), as defined previously, and the fluorescent dye(s) (b), as defined previously, are applied sequentially, i.e. successively. According to this other embodiment, the dyeing process is performed in at least two steps.

According to a first embodiment in at least two steps, the fluorescent dye(s) (b), as defined previously, are applied to the keratin fibres subsequently to the 2- or 4-azopyridinium dye(s) (a), as defined previously. In other words, the fluorescent dye(s) (b), as defined previously, are applied after the 2- or 4-azopyridinium dye(s) (a), as defined previously.

According to this first embodiment, the process for dyeing keratin fibres comprises at least the following two successive steps:

-   -   a first step of applying to said keratin fibres a cosmetic         composition comprising one or more 2- or 4-azopyridinium         dyes (a) chosen from the compounds of formula (I) or (II) as         defined previously, and also the optical isomers thereof, the         geometrical isomers thereof, the tautomers thereof, the organic         or mineral, acid or base salts thereof, the solvates thereof         such as hydrates, and mixtures thereof, followed by     -   a second step of applying to said keratin fibres a cosmetic         composition which comprises one or more fluorescent dyes (b), as         defined previously.

According to a preferred embodiment in at least two steps, the 2- or 4-azopyridinium dye(s) (a), as defined previously, are applied to the keratin fibres subsequently to the fluorescent dye(s) (b), as defined previously. In other words, the 2- or 4-azopyridinium dye(s) (a), as defined previously, are applied after the fluorescent dye(s) (b), as defined previously.

According to this preferred embodiment, the process for dyeing keratin fibres comprises at least the following two successive steps:

-   -   a first step of applying to said keratin fibres a cosmetic         composition comprising one or more fluorescent dyes (b), as         defined previously, followed by     -   a second step of applying to said keratin fibres a cosmetic         composition comprising one or more 2- or 4-azopyridinium         dyes (a) chosen from the compounds of formula (I) or (II) as         defined previously, and also the optical isomers thereof, the         geometrical isomers thereof, the tautomers thereof, the organic         or mineral, acid or base salts thereof, the solvates thereof         such as hydrates, and mixtures thereof.

Preferably, ingredients (a) and (b) are applied to the keratin fibres in a bath ratio that may range from 0.1 to 10 and more particularly from 0.2 to 8. For the purposes of the present invention, the term “bath ratio” means the ratio between the total weight of ingredient (a) or (b) and the total weight of keratin fibres to be treated.

When the dyeing process is performed in one step, ingredients (a) and (b) are advantageously left to stand on the keratin fibres for a time ranging from 1 to 90 minutes and more preferentially for a time ranging from 5 to 60 minutes.

When the dyeing process is performed in at least two steps, each of the ingredients (a) and (b) may be advantageously left to stand on the keratin fibres for a time ranging from 1 to 60 minutes and more preferentially for a time ranging from 5 to 50 minutes.

On conclusion of the dyeing process according to the invention, in one or at least two steps, the keratin fibres are advantageously rinsed with water. They may optionally be washed with a shampoo, followed by rinsing with water, before being dried or left to dry.

When the dyeing process is performed in at least two steps, the keratin fibres are advantageously rinsed with water between each step. In other words, the dyeing process may comprise an intermediate rinsing step between the application of the first ingredient and the application of the second ingredient. During this intermediate rinsing step, the keratin fibres may optionally be washed with a shampoo, followed by rinsing with water, before being dried or left to dry.

The dyeing process according to the present invention may be performed at room temperature (25° C.) or with heating.

When they are present, the reducing agent(s) may be applied separately or together with one of the ingredients (a) or (b). Preferably, when they are present, the reducing agent(s) are applied together with the ingredient (b).

When they are present, the oxidizing agent(s) may be applied separately or together with one of the ingredients (a) or (b). Preferably, when they are present, the oxidizing agent(s) are applied after the ingredients (a) and (b).

According to a particular embodiment, the process for dyeing keratin fibres according to the present invention comprises the following successive steps:

-   -   a first step of applying to said keratin fibres a cosmetic         composition comprising one or more 2- or 4-azopyridinium         dyes (a) chosen from the compounds of formula (I) or (II) as         defined previously, and also the optical isomers thereof, the         geometrical isomers thereof, the tautomers thereof, the organic         or mineral, acid or base salts thereof, the solvates thereof         such as hydrates, and mixtures thereof, followed by     -   a second step of applying to said keratin fibres a cosmetic         composition comprising one or more fluorescent dyes (b), as         defined previously, and one or more reducing agents, as defined         previously.

According to a particular embodiment of the dyeing process of the invention, no step of said process involves an oxidizing agent.

According to another advantageous embodiment of the dyeing process of the invention, no step of said process involves a reducing agent.

The dyeing process according to the present invention may be applied to wet or dry, preferably dry, keratin fibres.

The Multi-Compartment Device

The present invention also relates to a multi-compartment device comprising a first compartment containing one or more 2- or 4-azopyridinium dyes (a) chosen from the compounds of formula (I) or (II) as defined previously, and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof, and a second compartment containing one or more fluorescent dyes (b) as defined previously.

Use

A subject of the present invention is also the use of one or more fluorescent dyes (b), as defined previously, combined with one or more 2- or 4-azopyridinium dyes (a) chosen from the compounds of formula (I) or (II), as defined previously, and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof such as hydrates, and mixtures thereof, for the dyeing of light keratin fibres, especially human keratin fibres such as the hair, in chestnut-brown, dark chestnut-brown, brown, brown with a glint or even black, without using an additional dye other than (a) or (b).

According to a particular embodiment, the “keratin fibres” are human keratin fibres and more particularly the hair.

The examples that follow serve to illustrate the invention without, however, being limiting in nature.

EXAMPLES

In the examples that follow, all the amounts are given as weight percentages relative to the total weight of the composition, unless otherwise indicated.

I. Example 1: Sequential Application of 4-Azopyridinium Dye of Formula (I) Followed by Fluorescent Dye

a) Preparation of the Compositions

Compositions (A1) and (A2), comprising a 4-azopyridinium dye of formula (I) according to the invention, were prepared from the ingredients whose contents are mentioned in the table below.

Composition A1 Composition A2

5 × 10⁻³ mol —

— 5 × 10⁻³ mol Aqueous ammonia pH = 9-9.5 pH = 9-9.5 Water qs 100 qs 100 Colour in solution Dark blue Dark blue

Composition (B), comprising a fluorescent dye, was prepared from the ingredients whose contents are indicated in the table below.

Compo- sition B

5 × 10⁻³ mol Aqueous ammonia pH = 9-9.5 Water qs 100 Colour in solution Red-orange b) Procedure

Compositions (A1) and (A2) obtained above were applied to 0.5 g locks of hair containing 90% white hairs, in a bath ratio equal to 2.

After a leave-on time of 30 minutes at room temperature, the locks of hair were rinsed with water, washed with shampoo and dried under a hood for 5 minutes.

Composition (B), obtained above, was then applied to each of the locks of hair, in a bath ratio equal to 2.

After a leave-on time of 20 minutes at room temperature, the locks of hair were rinsed with water, washed with shampoo and dried under a hood for 5 minutes.

The colour of the locks was evaluated visually.

c) Results

The results of the colouring on the locks of hair containing 90% white hairs are given in the table below.

Locks dyed with Locks dyed with A1 + B A2 + B Colour after dyeing Black withh a bluish Black with a violet glint glint

The results obtained above show that the sequential application of a 4-azopyridinium dye of formula (I) according to the present invention and of a fluorescent dye makes it possible to obtain very intense and chromatic colours.

These results also show that the process according to the invention, using only two particular direct dyes, a 4-azopyridinium dye of formula (I) combined with a fluorescent dye, makes it possible to obtain black colours.

II. Example 2: Sequential Application of Fluorescent Dye Followed by 4-Azopyridinium Dye of Formula (I)

a) Preparation of the Compositions

Compositions (A1), (A2) and (B) were prepared from the ingredients mentioned in Example 1.

b) Procedure

Composition (B) obtained above was applied to 0.5 g locks of hair containing 90% white hairs, in a bath ratio equal to 2.

After a leave-on time of 20 minutes at room temperature, the locks of hair were rinsed with water, washed with shampoo and dried under a hood for 5 minutes.

Next, each of the compositions (A1) and (A2), obtained above, was then applied to each of the locks of hair, in a bath ratio equal to 2.

After a leave-on time of 30 minutes at room temperature, the locks of hair were rinsed with water, washed with shampoo and dried under a hood for 5 minutes.

The colour of the locks was evaluated visually.

c) Results

The results of the colouring on the locks of hair containing 90% white hairs are given in the table below.

Locks dyed with Locks dyed with B + A1 B + A2 Colour after Black with a bluish Black with a violet dyeing glint glint

The results obtained above show that the sequential application of a fluorescent dye and of a 4-azopyridinium dye of formula (I) according to the present invention makes it possible to obtain very intense and chromatic colours.

These results also show that the process according to the invention, using only two particular direct dyes, a 4-azopyridinium dye of formula (I) combined with a fluorescent dye, makes it possible to obtain black colours.

III. Example of Combined Application

a) Compositions

Compositions (C1) to (C4) were prepared from the ingredients whose contents are indicated in the table below.

C1 C2 C3 C4

5 × 10⁻³ mol — — —

— 5 × 10⁻³ mol — —

— — 5 × 10⁻³ mol —

— — — 5 × 10⁻³ mol

5 × 10⁻³ mol — — —

— 5 × 10⁻³ mol 5 × 10⁻³ mol 5 × 10⁻³ mol Aqueous ammonia pH = 9-9.5 pH = 9-9.5 pH = 9-9.5 pH = 9-9.5 Water qs 100 qs 100 qs 100 qs 100 b) Procedure

Each of the compositions (C1) to (C4) obtained above was applied to 0.5 g locks of hair containing 90% white hairs, in a bath ratio equal to 2.

After a leave-on time of 45 minutes at room temperature, the locks of hair were rinsed with water, washed with shampoo and dried under a hood for 5 minutes.

The colour of the locks was evaluated visually.

c) Results

The results of the colouring on the locks of hair containing 90% white hairs are given in the table below.

C1 C2 C3 C4 Colour after dyeing Black Black Orange- Black with a brown with a bluish violet glint glint

The results obtained above show that the process according to the invention makes it possible to obtain very intense and chromatic colours.

These results also show that the combination of only two particular direct dyes, i.e. a 4-azopyridinium dye of formula (I) combined with a fluorescent dye, makes it possible to obtain brown or black colours. 

The invention claimed is:
 1. A process for dyeing keratin fibres, comprising the application to said keratin fibres of the following ingredients: (a) one or more 2- or 4-azopyridinium dyes chosen from the compounds of formula (I) or (II) below, the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof, and mixtures thereof,

in which formulae (I) and (II): R₁ and R′₁, which may be identical or different, represent an optionally substituted linear or branched C₁ to C₆ alkyl radical; R₂ and R′₂, which may be identical or different, represent: a halogen atom, or a linear or branched C₁ to C₄ alkyl radical; R₃ and R′₃, which may be identical or different, represent, independently of each other: a C₁ to C₄ alkyl radical, a (di)(C₁-C₄)(alkyl)amino radical, a (C₁-C₄)alkylcarbonylamino radical, a hydroxyl radical, a halogen atom, a C₁ to C₄ alkoxy radical, a (C₁-C₄)alkylthio radical, or alternatively, two adjacent radicals R₃ or R′₃ together form a 6-membered aromatic ring optionally substituted with one or more hydroxyl or amino groups; R₄ and R′₄, which may be identical or different, represent: a (di)(C₁-C₄)(alkyl)amino radical, a hydroxyl radical, a C₁ to C₄ alkoxy radical, a radical —NR₅R₆, in which R₅ and R₆, which may be identical or different, represent, independently of each other: a linear or branched, optionally substituted C₁ to C₂₀ alkyl radical, or a phenyl radical, or alternatively, two radicals R₃ of formula (I) or R′₃ of formula (II) located, respectively, ortho to the group R₄ (formula (I)) or R′₄ (formula (II)) form, respectively, with R₅ and R₆ of the group R₄ (formula (I)) or of the group R′₄ (formula (II)) a 6- to 10-membered heterocycle optionally comprising one or more heteroatoms; m, m′, n and n′ are integers ranging from 0 to 4; Y represents an anionic counterion or a mixture of organic or inorganic anions which ensure the electrical neutrality of the compounds of formula (I) and/or (II); and (b) one or more fluorescent dyes; it being understood that the 2- or 4-azopyridinium dye(s) (a) and the fluorescent dye(s) (b) are applied to said keratin fibres together or sequentially.
 2. The process according to claim 1, characterized in that R₁ and R′₁, which may be identical or different, represent a linear C₁ to C₆ alkyl radical, optionally substituted with one or more hydroxyl groups.
 3. The process according to claim 1, characterized in that R₄ and R′₄, which may be identical or different, represent: an amino radical, or a radical —NR₅R₆, in which R₅ and R₆, which may be identical or different, represent, independently of each other: a linear or branched C₁ to C₆ alkyl radical, optionally substituted with one or more hydroxyl groups, or a phenyl radical.
 4. The process according to claim 1, characterized in that the dye(s) (a) are chosen from the compounds of formula (I) or (II) in which: R₃ and R′₃, which may be identical or different, represent, independently of each other: a C₁ to C₂ alkyl radical, an amino radical, an acylamino radical (—NHCOCH₃), a chlorine atom, a C₁ to C₂ alkoxy radical, or alternatively, two adjacent radicals R₃ or R′₃ together form a 6-membered aromatic ring optionally substituted with a hydroxyl or amino group, or alternatively, two radicals R₃ of formula (I) or R′₃ of formula (II) located, respectively, ortho to the group R₄ (formula (I)) or R′₄ (formula (II)) form, respectively, with R₅ and R₆ of the group R₄ (formula (I)) or of the group R′₄ (formula (II)) a 6- to 10-membered heterocycle comprising one or two heteroatoms; and R₄ and R′₄, which may be identical or different, represent: an amino radical, or a radical —NR₅R₆, in which R₅ and R₆, which may be identical or different, represent, independently of each other: a linear or branched C₁ to C₄ alkyl radical, optionally substituted with one or more hydroxyl groups, or a phenyl radical.
 5. The process according to claim 1, characterized in that the 2- or 4-azopyridinium dye(s) (a) are chosen from the following compounds, the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof, and mixtures thereof:

Y being as defined in claim
 1. 6. The process according to claim 1, characterized in that the fluorescent dye(s) (b) are chosen from the following dyes: acridines, acridones, azlactones, benzanthrones, benzimidazoles, benzimidazolones, benzindoles, benzoxazoles, benzopyrans, benzothiazoles, coumarins, difluoro{2-[(2H-pyrrol-2-ylidene-kN)methyl]-1H-pyrrolato-kN}borons, dipyrinones, diketopyrrolopyrroles, fluorindines, (poly)methines (especially cyanins and styryls/hemicyanins), naphthalimides, naphthanilides, naphthylamine (such as dansyls), naphtholactams, oxadiazoles, oxazines, perilones, perinones, perylenes, polyenes/carotenoids, squaranes, stilbenes, xanthenes, thioxanthenes, thiazines, and mixtures thereof.
 7. The process according to claim 1, characterized in that the fluorescent dye(s) (b) are direct dyes.
 8. The process according to claim 1, characterized in that the fluorescent dye(s) (b) are dyes which absorb light in the yellow, orange and red range.
 9. The process according to claim 1, characterized in that the fluorescent dye(s) (b) are dyes which comprise at least one cationic chromophore chosen from formulae (III), (IV), (IIIa) and (IVa) below: W⁺—[C(R^(c))═C(R^(d))]_(m′)—Ar′—(*)Q⁻  (III) Ar—[C(R^(d))═C(R^(c))]_(m′)—W′⁺—(*)Q⁻  (IV), in which formulae (III) and (IV): W⁺ represents a cationic heteroaryl group; W′⁺represents a divalent heteroaryl radical as defined for W⁺; Ar represents an aryl group; Ar′ is a divalent aryl radical as defined for Ar; m′ represents an integer between 1 and 4 inclusive; R_(c) and R_(d), which may be identical or different, represent a hydrogen atom or optionally a substituted (C₁-C₈)alkyl, or alternatively R_(c) is contiguous with W or W′ and/or R^(d) is contiguous with Ar or Ar′ and form, with the atoms that bear them, a (hetero)cycloalkyl; Q⁻ is an organic or mineral anionic counterion; (*) represents the part of the fluorescent chromophore that is bonded to the rest of the dye;

in which formulae (IIIa) and (IVa) R^(e), R^(f), R_(g) and R^(h), which may be identical or different, represent a hydrogen atom or a (C₁-C₆)alkyl group which is optionally substituted.
 10. The process according to claim 1, characterized in that the fluorescent dye(s) (b) are chosen from the dyes of formulae (V), (VI) and (VII) and also the organic or mineral, acid or base salts thereof, the optical isomers, geometrical isomers and tautomers thereof, and the solvates thereof:

in which formulae (V), (VI) and (VII): R₁ and R₂, which may be identical or different, represent a hydrogen atom or a C₁-C₆ alkyl group; G₁ represents a hydrogen atom or a group chosen from NH₂ and OH; R_(a), R′_(a), R″_(a), R′″_(a), R_(b), R′_(b), R″_(b) and R′″_(b), which may be identical or different, represent a) a hydrogen atom, b) a halogen atom, a group from among: c) amino, d) (C₁-C₄)alkylamino, e) (C₁-C₄)dialkylamino, f) cyano, g) carboxyl —C(O)OH or carboxylate —C(O)O⁻, Q⁺, h) hydroxyl —OH or alkoxide —O⁻Q⁺, i) (poly)halo(C₁-C₆)alkyl, j) acylamino, k) (C₁-C₆)alkoxy, l) (C₁-C₆)alkylthio, m) (poly)hydroxy(C₂-C₄)alkoxy, n) (C₁-C₆)alkylcarbonyloxy, o) (C₁-C₆)alkoxycarbonyl, p) (C₁-C₆)alkylcarbonylamino, q) acylamino, r) carbamoyl, s) (C₁-C₆)alkylsulfonylamino, t) aminosulfonyl, u) —SO₃H or sulfonate —SO₃ ⁻, Q⁺or v) (C₁-C₆)alkyl optionally substituted with a group chosen from (C₁-C₆)alkoxy, hydroxyl, cyano, carboxyl, amino, (di)(C₁-C₄)alkylamino, or alternatively the two alkyl radicals borne by the nitrogen atom of the amino group form a 5- to 7-membered heterocycle optionally comprising another nitrogen or non-nitrogen heteroatom; or alternatively two groups R_(a) and R′_(a); R_(b) and R′_(b) borne by two adjacent carbon atoms together form a benzo or indeno ring, a fused heterocycloalkyl or fused heteroaryl group; the benzo, indeno, heterocycloalkyl or heteroaryl ring being optionally substituted with a halogen atom, an amino, (C₁-C₄)alkylamino, (C₁-C₄)dialkylamino, nitro, cyano, carboxyl, hydroxyl or trifluoromethyl group, an acylamino, (C₁-C₄)alkoxy, (poly)hydroxy(C₁-C₄)alkoxy, (C₁-C₄)alkylcarbonyloxy, (C₁-C₄)alkoxycarbonyl or (C₁-C₄)alkylcarbonylamino radical, an acylamino, carbamoyl or alkoxyalkylsulfonylamino radical, an aminosulfonyl radical, or a (C₁-C₆)alkyl radical optionally substituted with: a group chosen from (C₁-C₆)alkoxy, hydroxyl, cyano, carboxyl, amino, (C₁-C₄)alkylamino and (C₁-C₄)dialkylamino, or alternatively the two alkyl radicals borne by the nitrogen atom of the amino group form a 5- to 7-membered heterocycle optionally comprising another nitrogen or non-nitrogen heteroatom; or alternatively, two groups R_(i) and R_(a); and/or a group R′_(i) and R′_(a) together form a fused (hetero)cycloalkyl; R_(g) represents a hydrogen atom, a (hetero)aryl(C₁-C₄)alkyl group or a (C₁-C₆)alkyl group that is optionally substituted; R_(e) represents a covalent bond, a linear or branched, optionally substituted (C₁-C₈)alkylene or (C₂-C₈)alkenylene hydrocarbon-based chain; R_(f) represents a hydrogen atom, a (C₁-C₄)alkoxy group, an amino group R₃R₄N—, a quaternary ammonium group M′, R₃R₄R₅N⁺— in which R₃, R₄ and R₅, which may be identical or different, represent a (C₁-C₄)alkyl group or R₃R₄N— represents an optionally substituted heteroaryl group, or alternatively M′, R₃R₄R₅N⁺— represents an optionally substituted cationic heteroaryl group; G represents i) a group —NR_(c)R_(d), ii) —OR with R representing a) a hydrogen atom, b) an optionally substituted, c) an optionally substituted (hetero)aryl group, d) an optionally substituted (hetero)aryl(C₁-C₆)alkyl group such as benzyl, e) optionally substituted (hetero)cycloalkyl, f) optionally substituted (hetero)cycloalkyl(C₁-C₆)alkyl; or alternatively when G represents —NR_(c)R_(d), two groups R_(c) and R′_(a) and/or R_(d) and R_(a) together form a saturated heteroaryl or heterocycle, optionally substituted with one or more (C₁-C₆)alkyl groups; R_(c) and R_(d), which may be identical or different, represent a hydrogen atom or a group from among: a) optionally substituted (hetero)aryl, b) optionally substituted (hetero)aryl(C₁-C₄)alkyl, c) optionally substituted (hetero)cycloalkyl, d) optionally substituted (hetero)cycloalkyl(C₁-C₄)alkyl, f) (C₂-C₅)alkyl or g) (C₁-C₈)alkyl which is optionally substituted, with a hydroxyl, carboxyl, carboxylate, sulfate or sulfonate group; or alternatively two adjacent radicals R_(c) and R_(d) borne by the same nitrogen atom together form an optionally substituted heterocyclic or optionally substituted heteroaryl group; R_(i) and R′_(i), which may be identical or different, represent a hydrogen atom or a (C₁-C₄)alkyl group;

represents a (hetero)aryl group fused to the phenyl ring; or alternatively is absent from the phenyl; m represents an integer between 1 and 18 inclusive; M′ represents an anionic counterion, derived from a salt of an organic or mineral acid, or from an organic or mineral base that ensures the electrical neutrality of the dye; Q⁺ represents a cationic counterion, derived from a salt of an organic or mineral acid, or from an organic or mineral base that ensures the electrical neutrality of the dye; it being understood that when the dye comprises a carboxylate, sulfonate or alkoxide group, then M′ and Q⁺ may be absent to ensure the electrical neutrality of said dye.
 11. The process according to claim 10, characterized in that the fluorescent dye(s) (b) are chosen from the styryl dyes of formula (VIII) below, and also the organic or mineral, acid or base salts thereof, the optical isomers, geometrical isomers and tautomers thereof, and the solvates thereof:

in which formula (VIII) G, G₁, R_(a), R′_(a), R″_(a), R_(b), R′_(b), R″_(b), R_(i), R′₁, R₁, R₂ and m are as defined in claim
 10. 12. The process according to claim 10, characterized in that the fluorescent dye(s) (b) are chosen from the styryl dyes of formula (IX) below, and also the organic or mineral, acid or base salts thereof, the optical isomers, geometrical isomers and tautomers thereof, and the solvates thereof:

in which formula (IX) G, G₁, R_(a), R′_(a), R_(b), R′_(b) and m are as defined in claim
 10. 13. The process according to claim 1, characterized in that the fluorescent dye(s) (b) are chosen from the compounds of formulae (X), (XI), (XII) and (XIII) below, and also the organic or mineral, acid or base salts thereof, the optical isomers, geometrical isomers and tautomers thereof, and the solvates thereof:

in which formulae (X), (XI), (XII) and (XIII): R₁, R², R³ and R⁴, which may be identical or different, represent a hydrogen atom or a (C₁-C₆)alkyl group; R⁵, R⁶, R⁷, R⁸ and R⁹, which may be identical or different, represent i) a hydrogen atom or ii) a halogen atom, iii) a group OR in which R represents a hydrogen atom or Q⁺, or a (C₁-C₃)alkyl group, a group from among iv) aryl, v) aryl(C₁-C₃)alkyl, vi) cyano, vii) nitro, viii) (C₁-C₃)alkylthio, ix) amino NR¹⁰R¹¹ with R¹⁰ and R¹¹, which may be identical or different, representing a) a hydrogen atom, b) a (C₂-C₄)alkyl group or c) a substituted (C₁-C₈)alkyl group; m represents an integer between 1 and 18 inclusive; M′ represents an anionic counterion derived from a salt of an organic or mineral acid, or from an organic or mineral base that ensures the electrical neutrality of the dye; Q⁺ represents a cationic counterion, derived from a salt of an organic or mineral acid, or from an organic or mineral base that ensures the electrical neutrality of the dye; it being understood that when the dye comprises an alkoxide group, then M′ and Q⁺ may be absent to ensure the electrical neutrality of said dye.
 14. The process according to claim 13, characterized in that the fluorescent dye(s) (b) of the invention are chosen from those of formulae (XIV) and (XV) below:

in which formulae (XIV) and (XV) R⁵, R⁷, R⁸ and m are as defined in claim 13 m represents an integer between 1 and 18 inclusive; and M′ represents an anionic counterion, derived from a salt of an organic or mineral acid, or from an organic or mineral base that ensures the electrical neutrality of the dye; it being understood that when the dye comprises an alkoxide group, then M′ and Q⁺ may be absent to ensure the electrical neutrality of said dye.
 15. The process according to claim 13, characterized in that the fluorescent dye(s) (b) are chosen from: the fluorescent dyes of formula (X) with: R¹ R² R³ R⁴ R⁵ R⁶ R⁷ R⁸ R⁹ m H H H H H H H H H 1 H H H H H t-Bu OH t-Bu H 5 H H H H H t-Bu OH t-Bu H 5 H H H H H H NH₂ H H 1 H H H H H H NH₂ H OCH₃ 1 H H H H H H OH Br H 5 H H H H H OCH₃ OH OCH₃ H 5 H H H H Cl H OH H Cl 5 H H H H H H OH H H 10 H H H H H OCH₃ OH OCH₃ H 10 H H H H H t-Bu OH t-Bu H 10 H H H H H H N(CH₂CH3)₂ H H 1 H H H H H H N(CH₂CH3)₂ H H 1 H H H H H H N(CH₂CH3)₂ H H 1 H H H H H t-Bu OH t-Bu H 10 H H H H H H N(CH₂CH₃)CH₂CH₂OH H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H N(CH₂CH₃)₂ H H 1 H H H H H H n-C₆H₁₃ H H 1 H H H H H H N(CH₂CH₂OH)₂ H H 2 H H H H H H N(n-Bu)₂ H H 2 H H H H H OCH₃ OH H H 10 H H H H H H OC₂H₅OH H H 1 H H H H H H OH H H 1 H H benzo H H H H H 1 H H benzo H H N(CH₂CH₂OH)₂ H H 1 H H benzo H H N(CH₂CH₂OH)₂ H H 1

and also the organic or mineral, acid or base salts thereof, the optical isomers, geometrical isomers and tautomers thereof, and the solvates thereof; the fluorescent dyes of formula (XI) with: R¹ R² R³ R⁴ R⁵ R⁶ R⁷ R⁸ R⁹ m CH₃ H H H OH H OCH₃ H H 2 CH₃ H H H H H OCH₃ OCH₂-Ph H 2 CH₃ H H H H H H H OCH₃ 2 CH₃ H H H F H H H H 2 CH₃ H H H H H H OPh H 2 CH₃ H H H H H N(CH₂CH₂OAc)₂ H H 2 CH₃ H H H OCH₃ H OCH₃ OCH₃ H 2 CH₃ H H H H H H CH₃ H 2 CH₃ H H H H H OH H H 2 CH₃ H H H H OCH₃ OCH₃ OCH₃ H 2 CH₃ H H H H OCH₃ OH OH H 2 CH₃ H H H H H OCH₃ OCH₃ OCH₃ 2 CH₃ H H H H H H OCH₃ OH 2 CH₃ H H H H H N(n-butyl)₂ H H 2 CH₃ H H H H OCH₃ OCH₃ H H 2 CH₃ H H H H H H H H 2 CH₃ H H H H H i-propyl H H 2 H H H H H H OH H H 6 H H H H H OCH₃ OCH₃ OCH₃ H 6 H H H H OH H OCH₃ H H 2 H H H H OCH₃ H H OCH₃ OCH₃ 2 H H H H H H H H Br 2 H H H H H H OH H H 2 H H H H OCH₃ OCH₃ OCH₃ H H 6 H H H H OH OCH₃ H H H 6 H H H H H OCH₃ OCH₃ H H 6 H H H H H OCH₃ OCH₃ H H 2 H H H H H H C(O)—OH H H 6 H H H H H H C(O)—OH H H 2 H H H H H H i-propyl H H 2 H H H H H H N(CH₃)CH₂CH₂CN H H 2 H H H H H H OCH₃ OCH₂Ph H 2 H H H H H H H OPh H 2 H H H H H H N(CH₂CH₂C(O)CH₃)₂ H H 2 H H H H OH H OCH₃ H H 6 H H H H H OCH₃ OCH₃ OCH₃ H 2 H H H H OCH₃ H OCH₃ OCH₃ H 6 H H H H H H H CH₃ H 2 H H H H H H N(CH₃)CH₂CH₂OH H H 2

and also the organic or mineral, acid or base salts thereof, the geometrical isomers and tautomers thereof, and the solvates thereof; the fluorescent dyes of formulae (X′) and (XI′):

with M′ as defined in claim 13; and R⁵ R⁷ R⁸ m R⁵ R⁷ R⁸ m H N(CH₂CH₂OH)₂ H 2 OCH₃ OCH₃ OCH₃ 2 H N(CH₂CH₂OH)₂ H 3 OCH₃ OCH₃ OCH₃ 3 H N(CH₂CH₂OH)₂ H 4 OCH₃ OCH₃ OCH₃ 3 H N(CH₂CH₂OH)₂ H 5 OCH₃ OCH₃ OCH₃ 4 H N(CH₂CH₂OH)₂ H 6 OCH₃ OCH₃ OCH₃ 5 H N(CH₂CH₂OH)₂ H 8 OCH₃ OCH₃ OCH₃ 8 H N(CH₂CH₂OH)₂ H 10 OCH₃ OCH₃ OCH₃ 10 H N(CH₂CH₂OH)₂ H 12 OCH₃ OCH₃ OCH₃ 12 H N(CH₂CH₂OH)₂ H 14 OCH₃ OCH₃ OCH₃ 14 H N(CH₂CH₂OH)₂ H 16 OCH₃ OCH₃ OCH₃ 16 H CH₃CH₂N(CH₂CH₂OH) H 2 H CH₃CH₂N(CH₂CH₂OH) H 4 and

and also the organic or mineral, acid or base salts thereof, the geometrical isomers and tautomers thereof, and the solvates thereof; the fluorescent dyes of formula (XII) with: R¹ R² R³ R⁴ R⁵ R⁶ R⁷ R⁸ R⁹ m H H H H H H OCH₃ OCH₃ OCH 2 H H H H OH OCH₃ H H H 2 H H H H H H H H H 2 H H H H H OCH₃ OCH₃ H H 2 H H H H OH H OH H H 6 H H H H OCH₃ H OCH₃ OCH₃ H 6 H H H H H H OH H H 6 H H H H OCH₃ H H H F 2 H H H H H H C(O)—OH H H 2 H H H H H H Isopropyl H H 2 H H H H H H N(CH₂CH₂C(O)CH₃)₂ H H 2 H H H H OH H OCH₃ H H 2 H H H H H H OH H H 2 H H H H H OCH₃ OH OH H 2 H H H H H CH₃ OCH₂Ph CH₃ H 2 H H H H H OCH₃ OCH₃ OCH₃ H 2 H H H H H OCH₃ OCH₃ OCH₃ H 6 H H H H H H N(CH₃)₂ H H 6 H H H H H H OCH₃ OCH₃ OCH₃ 6 H H H H H H Phenyl H H 6 H H H H H OCH₃ OCH₃ H H 6 H H H H H H C(O)—OH H H 6 H H H H H H N(n-Butyl)₂ H H 2 H H H H H H OCH₃ OCH₃ H 3 H H H H H H OCH₃ OCH₃ H 2 H H H H H H OCH₃ OCH₃ H 5 H H H H H H OCH₃ H H 3 H H H H H H N(CH₃)₂ H H 3 H H H H H H H H H 3

and also the organic or mineral, acid or base salts thereof, the optical isomers, geometrical isomers and tautomers thereof, and the solvates thereof; the fluorescent dyes of formula (XIII) with: R¹ R² R³ R⁴ R⁵ R⁶ R⁷ R⁸ R⁹ m CH₃ H H H OH H OCH₃ H H 2 CH₃ H H H H H OCH₃ OCH₂-Ph H 2 CH₃ H H H H H H H OCH₃ 2 CH₃ H H H F H H H H 2 CH₃ H H H H H H OPh H 2 CH₃ H H H H H N(CH₂CH₂OAc)₂ H H 2 CH₃ H H H OCH₃ H OCH₃ OCH₃ H 2 CH₃ H H H H H H CH₃ H 2 CH₃ H H H H H OH H H 2 CH₃ H H H H OCH₃ OCH₃ OCH₃ H 2 CH₃ H H H H OCH₃ OH OH H 2 CH₃ H H H H H OCH₃ OCH₃ OCH₃ 2 CH₃ H H H H H H OCH₃ OH 2 CH₃ H H H H H N(n-butyl)₂ H H 2 CH₃ H H H H OCH₃ OCH₃ H H 2 CH₃ H H H H H H H H 2 CH₃ H H H H H i-propyl H H 2 H H H H H H OH H H 6 H H H H H OCH₃ OCH₃ OCH₃ H 6 H H H H OH H OCH₃ H H 2 H H H H OCH₃ H H OCH₃ OCH₃ 2 H H H H H H H H Br 2 H H H H H H OH H H 2 H H H H H H N(CH₃)₂ H H 6 H H H H OCH₃ OCH₃ OCH₃ H H 6 H H H H OH OCH₃ H H H 6 H H H H H OCH₃ OCH₃ H H 6 H H H H H OCH₃ OCH₃ H H 2 H H H H H H C(O)—OH H H 6 H H H H H H C(O)—OH H H 2 H H H H H H i-propyl H H 2 H H H H H H N(CH₃)CH₂CH₂CN H H 2 H H H H H H OCH₃ OCH₂Ph H 2 H H H H H H H OPh H 2 H H H H H H N(CH₂CH₂C(O)CH₃)₂ H H 2 H H H H OH H OCH₃ H H 6 H H H H H OCH₃ OCH₃ OCH₃ H 2 H H H H OCH₃ H OCH₃ OCH₃ H 6 H H H H H H H CH₃ H 2 H H H H H H N(CH₃)CH₂CH₂OH H H 2 CH₃ H H H H H N(CH₃)₂ H H 2

and also the organic or mineral, acid or base salts thereof, the geometrical isomers and tautomers thereof, and the solvates thereof; and the fluorescent dyes of formulae (XII′) and (XIII′) below:

with: R⁵ R⁷ R⁸ m R⁵ R⁷ R⁸ m H N(CH₂CH₂OH)₂ H 2 OCH₃ OCH₃ OCH₃ 2 H N(CH₂CH₂OH)₂ H 3 OCH₃ OCH₃ OCH₃ 3 H N(CH₂CH₂OH)₂ H 4 OCH₃ OCH₃ OCH₃ 3 H N(CH₂CH₂OH)₂ H 5 OCH₃ OCH₃ OCH₃ 4 H N(CH₂CH₂OH)₂ H 6 OCH₃ OCH₃ OCH₃ 5 H N(CH₂CH₂OH)₂ H 8 OCH₃ OCH₃ OCH₃ 8 H N(CH₂CH₂OH)₂ H 10 OCH₃ OCH₃ OCH₃ 10 H N(CH₂CH₂OH)₂ H 12 OCH₃ OCH₃ OCH₃ 12 H N(CH₂CH₂OH)₂ H 14 OCH₃ OCH₃ OCH₃ 14 H N(CH₂CH₂OH)₂ H 16 and OCH₃ OCH₃ OCH₃ 16

and also the organic or mineral, acid or base salts thereof, the geometrical isomers and tautomers thereof, and the solvates thereof; with M′ Q⁺ as defined in claim
 13. 16. The process according to claim 1, characterized in that it also comprises the application to said keratin fibres of one or more reducing agents.
 17. The process according claim 1, characterized in that it does not use any reducing agent.
 18. The process according to claim 1, characterized in that the 2- or 4-azopyridinium dye(s) and the fluorescent dye(s) are applied together to said keratin fibres.
 19. The process according to claim 1, characterized in that it comprises at least the following two successive steps: a first step of applying to said keratin fibres a cosmetic composition comprising one or more fluorescent dyes followed by a second step of applying to said fibres a cosmetic composition comprising one or more 2- or 4-azopyridinium dyes (a) chosen from the compounds of formula (I) or (II), and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof, and mixtures thereof.
 20. The process according to claim 1, characterized in that it comprises at least the following two successive steps: a first step of applying to said keratin fibres a cosmetic composition comprising one or more 2- or 4-azopyridinium dyes (a) chosen from the compounds of formula (I) or (II) as defined in claim 1, and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof, and mixtures thereof, followed by a second step of applying to said fibres a cosmetic composition comprising one or more fluorescent dyes.
 21. The process according to claim 19, characterized in that it comprises at least two successive steps in which the pH of the cosmetic composition(s) is between 6 and 11 inclusive.
 22. A cosmetic composition comprising one or more 2- or 4-azopyridinium dyes (a) chosen from the compounds of formula (I) or (II), and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof, and mixtures thereof, and one or more fluorescent dyes (b), said composition optionally having a pH of between 6 and 11 inclusive, wherein the compounds of formula (I) or (II) are:

wherein: R₁ and R′₁, which may be identical or different, represent an optionally substituted linear or branched C₁ to C₆ alkyl radical; R₂ and R′₂, which may be identical or different, represent: a halogen atom, a linear or branched C₁ to C₄ alkyl radical; R₃ and R′₃, which may be identical or different, represent, independently of each other: a C₁ to C₄ alkyl radical, a (di)(C₁-C₄)(alkyl)amino radical, a (C₁-C₄)alkylcarbonylamino radical, a hydroxyl radical, a halogen atom, a C₁ to C₄ alkoxy radical, a (C₁-C₄)alkylthio radical, or alternatively, two adjacent radicals R₃ or R′₃ together form a 6-membered aromatic ring optionally substituted with one or more hydroxyl or amino groups; R₄ and R′₄ , which may be identical or different, represent: a (di)(C₁-C₄)(alkyl)amino radical, a hydroxyl radical, a C₁ to C₄ alkoxy radical, a radical —NR₅R₆, in which R₅ and R₆, which may be identical or different, represent, independently of each other: a linear or branched, optionally substituted C₁ to C₂₀ alkyl radical, or a phenyl radical, or alternatively, two radicals R₃ of formula (I) or R′₃ of formula (II) located, respectively, ortho to the group R₄ (formula (I)) or R′₄ (formula (II)) form, respectively, with R₅ and R₆ of the group R₄ (formula (I)) or of the group R′₄ (formula (II)) a 6- to 10-membered heterocycle optionally comprising one or more heteroatoms; m, m′, n and n′ are integers ranging from 0 to 4; Y represents an anionic counterion or a mixture of organic or inorganic anions which ensure the electrical neutrality of the compounds of formula (I) and/or (II).
 23. A multi-compartment device comprising a first compartment containing one or more 2- or 4-azopyridinium dyes chosen from the compounds of formula (I) or (II), and also the optical isomers thereof, the geometrical isomers thereof, the tautomers thereof, the organic or mineral, acid or base salts thereof, the solvates thereof, and mixtures thereof, and a second compartment containing one or more fluorescent dyes, wherein the compounds of formula (I) or (II) are:

wherein: R₁ and R′₁, which may be identical or different, represent an optionally substituted linear or branched C₁ to C₆ alkyl radical; R₂ and R′₂, which may be identical or different, represent: a halogen atom, a linear or branched C₁ to C₄ alkyl radical; R₃ and R′₃, which may be identical or different, represent, independently of each other: a C₁ to C₄ alkyl radical, a (di)(C₁-C₄)(alkyl)amino radical, a (C₁-C₄)alkylcarbonylamino radical, a hydroxyl radical, a halogen atom, a C₁ to C₄ alkoxy radical, a (C₁-C₄)alkylthio radical, or alternatively, two adjacent radicals R₃ or R′₃ together form a 6-membered aromatic ring optionally substituted with one or more hydroxyl or amino groups; R₄ and R′₄, which may be identical or different, represent: a (di)(C₁-C₄)(alkyl)amino radical, a hydroxyl radical, a C₁ to C₄ alkoxy radical, a radical —NR₅R₆, in which R₅ and R₆, which may be identical or different, represent, independently of each other: a linear or branched, optionally substituted C₁ to C₂₀ alkyl radical, or a phenyl radical, or alternatively, two radicals R₃ of formula (I) or R′₃ of formula (II) located, respectively, ortho to the group R₄ (formula (I)) or R′₄ (formula (II)) form, respectively, with R₅ and R₆ of the group R₄ (formula (I)) or of the group R′₄ (formula (II)) a 6- to 10-membered heterocycle optionally comprising one or more heteroatoms; m, m′, n and n′ are integers ranging from 0 to 4; Y represents an anionic counterion or a mixture of organic or inorganic anions which ensure the electrical neutrality of the compounds of formula (I) and/or (II). 